References
- Invariance Theory, the Heat Equation, and the Atiyah-Singer Index theorem (2nd edition), ISBN 0-8493-7874-4 P. B. Gilkey
- Illinois J. Math v.40 Riemannian submersions which preserve the eigne forms of the Laplacian P. B. Gilkey;. H. Park
- Bull. Korean Math. Soc. v.27 The Laplace-Beltrami operator and Riemannian submersion with minimal and not totally geodesic fibers J. H. Park
- Honam Mathermatical Journal v.16 A note on eigenfunctions of the Laplacian of warped products J. H. Park
- Kyungpook Math. J. v.35 A note on the eigenfunctions of the Laplacian for twisted products J. H. Park