Hughes, D. R., & Piper, F. C. (1973). Projective planes. Springer-Verlag.

Hughes, D. R., and F. C. Piper. Projective Planes. Nueva York: Springer-Verlag, 1973.

Hughes, D. R., and F. C. Piper. Projective Planes. Springer-Verlag, 1973.