APA (7th ed.) Citation

Croft, H. T., Guy, R. K., & Falconer, K. J. (1991). Unsolved problems in geometry. Springer-Verlag.

Chicago Style (17th ed.) Citation

Croft, Hallard T., Richard K. Guy, and K. J. Falconer. Unsolved Problems in Geometry. New York: Springer-Verlag, 1991.

MLA (9th ed.) Citation

Croft, Hallard T., et al. Unsolved Problems in Geometry. Springer-Verlag, 1991.