APA (7th ed.) Citation

Fenchel, W. (1989). Elementary geometry in hyperbolic space. Walter de Gruyter.

Chicago Style (17th ed.) Citation

Fenchel, W. Elementary Geometry in Hyperbolic Space. Berlin: Walter de Gruyter, 1989.

MLA (9th ed.) Citation

Fenchel, W. Elementary Geometry in Hyperbolic Space. Walter de Gruyter, 1989.