1. Introduction
As technology evolves, virtual reality (VR) has been applied in fields like entertainment, sports, education, games, medical, military, etc. The reason that VR is referred to as a high-potential medium in various fields is due to its nature that enables the user to experience life-like events using real-time simulation and interaction through multiple sensory channels that create ‘Presence’ [1,2]. Presence is defined as an idea of transportation i.e., the subjects who experience immersive media in various experiments report a sensation of being in a virtual world [2]. Particularly, the efficiency of VR in education and training is confirmed through many pieces of research [3]. According to Hu-Au & Lee [4], VR is beneficial in providing opportunities, increasing student engagement, providing constructivist (i.e., allowing students to construct their own knowledge from meaningful experiences.), authentic experiences to impact student’s identity; allowing new perspective-taking, empathy and supporting creativity and the ability to visualize complicated models hence its preference among young students. Virtual environments (VEs) can support trainees to learn through their experiences by offering rich, interactive and engaging educational content [5].
Various studies have focused on the effectiveness and applications of VR in education and training [6]. Constructivism theory suggests that humans construct knowledge and meaning based on their experiences. i.e. they build their knowledge upon the foundation of their previous learning [7]. Experiencing things and reflecting on those experiences is referred to as ‘First-person experience’; ‘Second-person experience’ is described by someone else, while ‘Third-person experience’ is experienced through a person’s interaction with a computer via the interface. However, the immersion and interaction via VR makes the psychological process of the third-person learner as the first person [3]. In skill development training, direct physical interaction between the object and the trainee is required. In this research, skill development training is defined through physical activity, a part of learning which entails moving one’s body part to accomplish some tasks. The movement of hands, legs, and body muscle is required while performing any work. Skill development training is associated with the kinesthesia ability to sense motion of limb or joint, also known as sensation or perception of movement. According to the research on Kinesthetic memory by Clark and Horch, humans have a remarkable ability to remember the position of their limbs quite accurately for long periods of time [8]. Our bodies detect how to perform a task and ultimately adopts the movements involved in performance of the task. The trainee moves his limbs based on the type of sensors and haptics utilized during the training through VR interactive content. Thus, the trainee is able to adapt the movement and recall the movements later. In industries, training constructs the proficiency of all the employees to perform the job in an effective manner. It supplies enough potentiality to the employees, holding future positions in an organization, reducing defects and performing effectively in job-related tasks. Training is also considered as a form of investment by corporations since it generates a lot of profit as investment returns and helps to establish its superiority [9]. This research will review VR projects and studies regarding the experiment to enhance the learning effects via VR in addition to analyzing their results. Six kinds of research were collected in four different areas and projects from 2009 to 2018. These projects show the use of VR in various fields of skill development training and their advantages. Those references are well described and have rich information to identify what should be learned from the projects. After the review, we suggest the benefits of adopting VR for skill development training, the field in which the project/research utilized VR for skill development training, and the factors for design consideration by comparing the training in the virtual and real-world in those projects.
2. VR Projects for Skill Development Training
2.1 Medical training VR
2.1.1 VR based simulators for training in Regional Anesthesia:
The methods of training involved in Regional Anesthesia (RA) include video teaching, ultrasound guidance and simulators [10]. The traditional training techniques of RA involves 'see one do one' method i.e., trainees work under the direct supervision of a senior and experienced surgeons which is time-consuming, costly, and variable in effectiveness [11]. In 2009, O. Grottke et al. developed a VR based simulator that allowed trainees to practice their technical skills via RA adopting various anatomies of patients in the virtual world [10].
The simulator application adopts several modules for collision detection, humanoids, interaction and visual implementation of the virtual toolkit ViSTA. A customized haptic input device is also implemented and utilized for palpation in order to localize the needle injection site realistically for needle operation as shown in figure 1. This application uses multimodal representations of both visual and basic haptics with intuitive interactions and a plausible simulation, creating a flexible training environment without endangering the patients. This simulator adopts a segmented algorithm allowing it to be used in different peripheral nerve blocks giving a wide range of anatomical variety of individual anatomy and for different anatomical regions.
Figure 1. Picture representing RA1 simulator application with VR based setup. The trainee controls the virtual needle using a PHANTOM Omni Haptic device2 [10].
2.2 Industry (Employee) training VR
2.2.1 Head-mounted display-based intuitive Virtual Reality training system for the mining industry:
The mining industry is a high-risk sector and requires plenty of training to ensure safety [13]. Drilling training for miners in the real environment is too risky. The drilling risks in regards to training include physical damage to equipment, physical harm to the trainee, loss of reputation in business etc. [14].
In 2016, Zhang Hui developed a Head-mounted display-based intuitive virtual reality training system for the mining industry [12]. This project was designed for underground mines drilling scenario training through employing an HMD [VR headset, a smartphone (Nexus 6P smartphone)] and a leap motion device with an HMD based intuitive type VR training system prototype. The user interacts with the virtual scene by moving hands and perform drilling activities. Sophisticated movements and gestures for drilling can be performed by the user inside the virtual environment, manipulating the virtual miner’s hand as shown in figure 2. An experiment was then conducted with 10 trainees using both HMD and screen-based general training systems. The use of HMD based training was compared with the screen-based and subsequently the joystick and wearable sensors. The comparison conducted was based on the answers from questionnaires about the levels of immersion, intuitive, interaction, ease of use and ease of learning. The score of HMDs based training was higher in all questions. In the case of immersion HMD based training, it had a score of 4.5 out of 5 while the screen-based training had a score of 1.5 which made a huge difference. The comparison suggested that the HMD based training system using VR is intuitive, interactive, immersive and easy to use. However, the drawback was that the wearable sensors could not provide a sense of touch to the user.
Figure 2. Picture representing RA simulator application with VR based setup. The trainee controls the virtual needle using a PHANTOM Omni Haptic device [13].
2.3 Safety Instruction Training VR
2.3.1 Virtual Reality Simulator for Advanced Cardiac Life Support Training:
Advanced Cardiac Life Support Training (ALCS) is a life-saving matter which is a time-sensitive and clinical team-based procedure adopted by people with respiratory failures [15]. The real-life environment entail high stress and time-critical scenario and the training includes a lecture and simulation practice using devices like Heartsome and Anne Manikin [16]. Vankipuram developed a Virtual Reality Simulator for ACLS in 2014 [15]. It provides an inspiring, engaging and role-playing virtual environment for the trainee.
It is a time-critical and team-based medical scenario platform for guiding trainees in aid for respiratory failure. The project primarily focuses on distance training, coordination, teamwork, and leadership. Six trainees can participate at a single time. Each trainee has a specific role such as Leader, compressor, medication, defibrillator, respiratory, and airway manager. The team is required to perform activities that assist them to coordinate as a team in order to save the patient as illustrated in figure 3. For the usability testing of the system, 96 ALCS certified clinicians are recruited and organized into 16 teams of 6 people each. The 16 teams were further divided into two groups: one having persuasive features and the other with limited persuasive features. Likert scale was utilized to measure the mean score comparison 1-5 (1-strongly negative 5-strongly positive) based on easy-to-use and usability through use of questionnaires. The minimally persuasive group exceeds the level as compared to that of the persuasive group by p = 0.00813 and p = 0.0944, respectively. The disadvantages included distraction of user by the communication indicator and global message on the screen, the simulator does not inform the result that the patient is saved or not, and lack of real-time performance experience of the user due to the absence of validating scoring technique for ACLS procedures. However, this project provides immersion, and remote location.
Figure 3. 1 shows the CPR role, 2 is the haptic joystick setup for CPR and picture 3 shows text-based feedback message black front (global message) and yellow font (team message) [15].
2.3.2 Application of VR in Disaster Response Training (Fire Safety):
Despite the numerous training programs and schools for fire-fighters, fire safety drills for common people are rarely conducted and the available training mostly includes case studies, face to face lectures and fire drills [17]. In 2018, Rajit Pimpale developed a VR Application for Disaster Response Training [18].
The project was developed to adequately prepare a disaster response team compared to training in a classroom or instructional learning. It also assists to reduce trauma for the responder. This project is a game where the trainee (player) wears a VR device, and assumes the role of a person encountering a specific disaster (fire) as in figure 4. The trainee has the freedom to perform certain actions, which determines whether the trainee survives the disaster or not. There are also some non-interactive and visible interactive objects which interact with the player creating real-time experience of the disaster (Interactive objects are those which interact with the users’ behavior). The trainee will face either consequences or benefits for their decision in the game which helps trainees to learn what they should do times of disaster and how they should handle the situation. This project concludes that apart from being immersive and entertaining, VR provides a better training platform for disaster management strategies giving realistic experiences to the user.
Figure 4. Fire propagation series scene in the project [18]
2.3.3 Effects of interface on procedural skill transfer in virtual training:
Lifeboat launching is a sophisticated process of transferring a tucked lifeboat to water that requires procedural skills, collaboration and synchronization of several roles thus, training is required [19]. In real life training, the subjects cannot always launch the lifeboat for safety reasons [20]. Traditionally, the training procedure entails instructional manuals, lectures, textbooks, and practical training in the real environment using real equipment [21].
Figure 5. Virtual training interfaces used in the experiment are shown: (a) monitor, keyboard and mouse, (b) head-mounted display and joy pad, (c) head-mounted display and wearable sensors. 2 is the sequential screenshots of the virtual training with guiding instructions. 3 is the evaluation of the VR training later in a real lifeboat [20].
The evaluation was based on comparing the ability of the participants to launch a lifeboat without mistakes in a real boat prior and after training. The technical skill scores of the participants using VR training with the wearable sensors group improved from 4.375 to 11.75 making it the highest. The conclusion was that VR training alone is enough for a training format involving short sessions (15-min sessions). However, for long sessions as a result of spatial representation of 3D text, there is a reduction in the information conveyance to the trainee.
2.4 Personal development VR
2.4.1 A VR dance training system using motion capture technology:
In real life dance training, it’s hard to manage training, location and the precise time when the teachers and students attend lessons [22]. In the case where the teacher is absent, the trainee can also learn by watching videos, but there is lack of feedback. The conventional process of coaching the dance incorporates the handy tools for training dance artists. During the process of learning, the dance artists may end up injured and frustrated, which can be an overwhelming hurdle [23]. Choreographers would shout and scream when the trainee doesn’t perform well, promoting fear in the dance studio among the students [24]. Consequently, decreasing the level of confidence among the trainees will hinder them from reaching their full potential.
In 2011, Chan et al. developed a VR dance training system using motion capture technology [22]. In this system, users should wear motion capture systems, and follow the movements of a virtual teacher, and then receive feedback on how to improve their movements. This project utilizes motion capture technology and motion analysis methods. This system conveys a complete analysis including the users' whole-body motion. After a successful comparative analysis between two motions, feedbacks are returned as shown in figure 6. During the evaluation, the students were asked to train in the system by watching the demo, practicing, and understanding the feedback. Teachers also made use of the system, assisting in the preparation of teaching materials by having their dance motions captured. 8 male students aged 21-30, who were students of the City University of Hong Kong were randomly selected to participate in the study randomly as the experimental and control group, consisting of 4 people per group (Experimental group participated in this project; Control group utilizes self-learning by watching method). Achievements for the learning outcomes: The mean and standard deviation of the skills were tested. The increase in the mean suggests that the training system is effective in the case of learning outcomes. Arousing interest in participants: The question for whether the project was interesting achieved a score of 2 out of 4 and for recommending other students to try the program scored 3 out of 4 making the project interesting. Subjects made an evaluation that the project was useful in guiding the students to correct direction and encouraged them to learn more. Also, the experiment results showed that this system assisted the students better in learning compared to the traditional approach of “watching video”. In the future, there are plans to incorporate additional features like feedback based on emotion and HMD. This application does not evaluate emotion. There is no realistic background to provide better immersion. Because of the screen-based display, this project is not fully immersive especially when the user needs to turn, hence, the user requires a VR HMD in order to experience full immersion.
Figure 6. In 1 subject is learning a dance motion watching the virtual teacher and 2 is the score report [22]
3. The Efficiency of Virtual Reality
In this study, training in the projects is compared with the real work environment and the differences between them are identified. After the analysis three factors from quantitative analysis, one factor from qualitative analysis, and three other factors added by the authors based on the nature of VR interface that has the telepresence [25] were identified. In Table 1 presents the Projects with their qualitative scores in specific factors. Similarly, Table 2 presents the comparison between the skill development training in the real and virtual environment based on the above key factors.
Table 1. Projects with their qualitative scores in specific factors
Table 2. Factors to compare the projects in Real and Virtual Environments
Thus, the results can be used to the advantage of VR application in skill development training and the points that must be emphasized to make the VR training more effective. The comparison is done based on the following factors:
1. Preps:
It deals with the kind of devices and equipment used in the project. Therefore, the types of devices used for the training are mentioned here.
2. Self-learning:
It visualizes the possibility for the users to undertake the training alone in the absence of an instructor. The self-learning functionality can also make the training system more effective.
3. Feedback providing:
This point is used to observe whether the system has feedback providing facility or not. Feedbacks makes the user evaluate his/her performance level and encourages him/her to expertise his skills. The feedback functionality makes the user learn more and evaluate themselves which makes them eager to perform better next time.
4. Safety:
This point illustrates the safety features of the training system and how safe it is for the trainee to perform.
5. Location-dependence:
This point is used to find out whether the project is dependent on the location for training or it can be performed anywhere in the area suitable to the user. The less location-dependent the training system is, the better as it helps in managing the training faster.
6. Time-dependence:
This point is used to observe how much time is consumed in managing the training. The less the time consumed for management, the better the training system.
7. Reversibility:
This explains whether the project is reversible or not. Generally, during the training process, lots of destruction and mistakes may happen. Some of them can be reversed to their previous form while others are irreversible. Therefore, it should be observed.
4. Result and Discussion
After comparison, the study derives a conclusion for every point explaining their role and effectiveness.
1. Preps:
In the real world the trainee uses various equipment and devices which might be large in numbers and sometimes impossible to manage. However, in VR the devices are virtual, and the trainee only needs HMD, haptics and sensors to manipulate those virtual devices. The haptics and sensors are comparatively easier to manage. The use of appropriate haptics assists in making the VR more immersive, interactive, interesting, engaging, easy to use and learn. It's very productive in learning technical skills but weaker in learning procedural skills as compared to keyboard and mouse. This is because Keyboard and mouse are common and familiar with the users, but the VR interactive contents are new and still under the evolution phase. Another drawback is that in real environment, devices have the feeling of touch, which cannot be replicated in a virtual environment.
2. Self-learning:
In a real environment the trainee has an instructor who instructs the user how to perform the task and is always there to guide. In the absence of the instructor, the trainee may conduct self-learning, which is too difficult. There are chances of trouble and accidents which might lead to massive destruction. Therefore, the trainee always needs to seek the instructor. However, this is possible in the VR environment since the application can guide, interact and evaluate the trainee and the results of learning effects, easy to learn and easy to use are successful.
3. Feedback providing:
In the real environment, the trainee gets feedback from the instructor which assists him to evaluate his overall performance. There are various kinds of feedback that are used in VR interactive content. These includes the evaluation feedback, guiding feedback and interactive feedback. Evaluation feedback is evaluating the skill of trainees based on their performance. It will encourage the trainee to try the training again in order to achieve better scores making him/her more addictive and evaluate their skill. Guiding feedback refers to the action of guiding the trainee to perform the task e.g. Text-based guidelines on-screen, Audio guidelines.
4. Location-dependence:
Almost every training in the real-world is location dependent. Mostly a specific location for training is required, which is hard to manage at all time. Conversely, with the use of a VR training system the user can solve the location-dependent problem since the VR training system is not location dependent. The trainee can train in any desired location using the VR contents provided.
5. Time-dependence:
VR projects solve the problem of time dependency as they reduced the time spent searching for instructors, tools, staff, safety and budget management that is present in real-world training.
6. Safety:
The real environment has a lot of risks and chances of accidents. In the case of medical or surgical training, the subject (patient) bears the risk. Similarly, in other training, the trainee bears the risk which can be life threatening. In VR, the environment, patient and tools are virtual 3D meshes such that the accidents are just inside the VR game, which makes training in VR safe.
7. Reversibility:
The real environment training, when the trainee makes some mistakes or damages during the training session it cannot be rebuilt, or the rebuilding takes time, but in VR everything is reversible since the objects are virtual 3D meshes.
The training in the real environment provided less opportunities and had the problems related to self-learning, location, time, safety, reversibility and preps. However, the VR projects simplified the training. The tools and subjects are all 3D animated meshes thus, only the VR HMD and haptics are required for the training. The training can be conducted in any location inside the room safely. The training can be conducted in the absence of an instructor because the system provides guiding, interactive and evaluation feedback making the training more interesting, motivating, easy to learn and use, safe, reversible, timesaving and location independent. Therefore, every key factors of skill development training using VR serves as an opportunity provider as shown in figure 7.
Figure 7. In Flowchart illustrating the advantages of VR
5. Result and Discussion
In this paper, we reviewed the journal papers on VR based skill development training systems and related projects from 2009 to 2018, the advantage and the factors that must be emphasized prior to developing an interactive skill development training content were then highlighted. After observing all the projects, conclusion was then drawn that the common advantages of VR in skill development training include three factors: Preps, Self-learning and Feedback providing from quantitative analysis, Safety from qualitative analysis in addition to 3 other factors, Time-dependence, Location-dependence and Reversibility based on the nature of VR interface that has telepresence. Selecting VR skill development training system will help reduce the demand of tools, location, time, instructor as it applies 3d models and animated meshes and instead will require VR HMD and haptics. Feedbacks provide guidance and encouragement for the trainees to practice more, evaluate their skills and motivate themselves with an aim to perform better hence, repeat the process. Since the trainees can evaluate themselves, it also promotes self-learning. However, excessive feedbacks may distract the trainee from performing the task thus, the developer must have the endeavor to limit the feedback contents. Thus, when developing a VR project for skill development training that requires physical activities and stepwise procedural learning, the developer needs to focus more on the key factors such as Self- learning, Feedback providing and Preps. VR as applied to skill development training also has some limitations including: locomotion sickness when there is longer exposure to VR contents and lack of vision in regards to the surroundings while using VR. Therefore, developing a short-session VR training system will be productive. It is a novel interactive system with evolving haptic devices such that users require time to adapt to the system.
Making the VR training system more immersive requires addition of simulation via haptic devices. However, haptics only are not enough to give the users a sense of touch as the real object does. Therefore, it is crucial to develop more advanced haptics for more immersive experience which would offer a new research direction.
Conflicts of Interest
The authors declare that there is no conflict of interest regarding the publication of this article.
References
- Mihai Duguleana, Adrian Nedelcu, and Florin Barbuceanu, "Measuring eye gaze convergent distance within immersive virtual environments," Procedia Engineering, vol. 69, pp. 333-339, 2014, doi: https://doi.org/10.1016/j.proeng.2014.02.240.
- Matthew Lombard and Theresa Ditton, "At the Heart of it all: The concept of presence," Journal of Computer Mediated Communication, vol. 3, issue. 2, 1997, doi: https://doi.org/10.1111/j.1083-6101.1997.tb00072.x.
- Dorota Kaminska, Tomasz Sapinski, Slawomir Wiak, Toomas Tikk, Rain Eric Haamer, Ergils Avots, Ahmed Helmi, Cagri Ozcinar, and Gholamreza Anbarjafari, "Virtual Reality and Its Applications in Education: Survey," Information, vol. 10, issue. 10, 2019, doi: https://doi.org/10.3390/info10100318.
- Elliot HU-Au and Joey J. Lee, "Virtual Reality in education: a tool for learning in the experience age," International Journal of Innovation in Education, vol. 4, no. 4, pp. 215-226, 2017, doi: https://doi.org/10.1504/IJIIE.2017.091481.
- Mantovani Fabrizia, VR learning: Potential and challenges for the use of 3D environments in education and training, Towards Cyberpsychology: Mind Cognitions and Society in the Internet Age, Amsterdam: ISO Press, no. 12, pp. 207-225, 2011.
- Veronica S. Pantelidis, "Reasons to use virtual reality in education and training courses and a model to determine when to use virtual reality," Themes in Science and Technology Education, vol. 2, pp. 59-70, 2009.
- Dr. BADA and Steve Olusegun, "Constructivist Learning Theory: A paradigm for teaching and learning," IOSR Journal of Research & method in Education, vol. 5, issue. 6, pp. 66-70, 2015, doi: 10.9790/7388-05616670.
- F. Clark and K. Horch, Kinesthesia, Handbook of Perception and Human Performance v.1 Sensory Processes and Perception, New York: Wiley-Interscience, vol. 1, pp. 1-62, 1986.
- L. Maharani and I. Nurnida, "The effect of training on employees' performance," Journal of Secretary and Business Administration, vol. 2, no. 2, pp. 52-59, 2018, doi: https://doi.org/10.31104/jsab.v2i2.49.
- O. Grottke, A. Ntouba, S. Ullrich, W. Liao, E. Fried, A. Prescher, T. M. Deserno, T. Kuhlen, and R. Rossaint, "Virtual reality-based simulator for training in regional anaesthesia," British Journal of Anaesthesia, vol. 103, issue. 4, pp. 594-600, 2009, doi: https://doi.org/10.1093/bja/aep224.
- Ahtsham U. Niazi, Philip W. Peng, Melissa Ho, Akhilesh Tiwari, and Vincent W. Chan, "The future of regional anesthesia education: lessons learned from the surgical specialty," Canadian Journal of Anesthesia, vol. 63, pp. 988-972, 2016, doi: https://doi.org/10.1007/s12630-016-0653-7.
- Alehandro Jarillo-Silva, Omar A. Domingue-Ramiez, Vicente Parra-Vega, and J. Patrico Ordaz-Oliver, "PHANToM OMNI Haptic device: kinematic and Manipulability," Electronics, Robotics and Automotive Mechanics Conference, pp. 193-198, 2009, doi: https://doi.org/10.1109/CERMA.2009.55.
- Zhang Hui, "Head-mounted display-based intuitive virtual reality training system for the mining industry," International Journal of Mining Science and technology, vol. 27, issue. 4, pp. 717-722, 2017, doi: https://doi.org/10.1016/j.ijmst.2017.05.005.
- Lilian A. Okwiri, "Risk Assessment and Risk Modelling in Geothermal Drilling," M.S. thesis, Dept. of Sustainable Energy Engineering, Iceland School of Energy, Ryejavik University, 2017.
- Akshay Vankipuram, Prabal Khanal, Aaron Ashby, Mithra Vankipuram, Ashish Gupta, Denise DrummGurnee, Karen Josey, and Marshall Smith, "Design and Development of a Virtual Reality Simulator for Advanced Cardiac Life Support Training," IEEE journal of Biomedical and Health Informatics, vol. 18, no. 4, pp. 1478-1484, 2014, doi: https://doi.org/10.1109/JBHI.2013.2285102.
- Polpun Boonmak, Suhattaya Boonmak, Somyong Srichaipanha, and Sujettana Poomsawat, "Knowledge and Skill after Brief ALCS Training," J Med Assoc Thailand, vol. 87, no. 11, pp. 1322-1314, 2004.
- Paul H.Lee, Baoguo Fu, Wangting Cai, Jingya Chen, Zhenfei Yuan, Lifen Zhang, and Xiuhong Ying, "The effectiveness of an on-line training program for improving knowledge of fire prevention and evacuation of healthcare workers: A randomized controlled trial," Plos One, 2018, doi: https://doi.org/10.1371/journal.pone.0199747.
- R. Pimpale, N. Prabhajaran and R. Kannadasan, "Application of VR in disaster response training," in Special Issue on ICAC SET'18, V. Kannan, E. Ramaraj and N. Venkatesan, Eds., vol. 119, no. 7, pp. 303-306, 2018.
- Min Jiang, Wei Lan, Jian Chang, Mark Dodwell, Jeremy Jekins, Hui Jun Yang, Ruo Feng Tong, and Jian Jun Zhang, "A game prototype for understanding the safety issues of a life boat launch," Virtual Reality, vol. 22, issue. 2, pp. 137-148, 2018, doi: https://doi.org/10.1007/s10055-018-0334-7.
- Jinki Jung and Young Joong Ahn, Effects of interface on procedural skill transfer in virtual training Lifeboat launching operation study, Wiley, 2018, doi: https://doi.org/10.1002/cav.1812.
- Kenichi Sasayama, JSMQA lifeboat 7 Launching Application Maintenance Engineering Training Course, Japan Ship-Machinery Quality Control Association, 2017.
- Jacky C. P. Chan, Howard Leung, Jeff K. T. Tang, and Taku Komura, "VR dance training system using motion capture technology," IEEE Transactions on Learning Technologies, vol. 4, issue. 2, pp. 187-195, 2010, doi: 10.1109/TLT.2010.27.
- Donna Krasnow and Steven J. Chartfield, "Dance Science and the Dance Technique Class," Impulse, vol. 4, pp.162-172, 1996.
- Sho Botham, "Ethical Issues in the Training and Developing of Dance Teachers in the Private Sector," Ph.D. dissertation, Dept. of Philosophy, University of Brighton, 2012.
- Jonathan Steuer, "Defining Virtual Reality: Dimensions Determining Telepresence," Journal of Communication, vol. 42, pp. 73-93, 1992, doi: https://doi.org/10.1111/j.1460-2466.1992.tb00812.x.