References
- Invariant Theory, Old and New Dieudonne, J.A.;Carrell, J.B.
- Invariant Theory Foggarty, J.
- Amer. Math. Monthly v.88 Rigid motions of conics: An introduction to invariant theory Grosshans, F.D.
- Amer. Math. Monthly v.94 no.9 Hyperbolic motions of conics Mendes, C.M.;Ruas, N.A.S.