APA (7th ed.) Citation

Fenchel, W. (2011). Elementary Geometry in Hyperbolic Space (Originally published 1989.). De Gruyter. https://doi.org/10.1515/9783110849455

Chicago Style (17th ed.) Citation

Fenchel, Werner. Elementary Geometry in Hyperbolic Space. Originally published 1989. Berlin: De Gruyter, 2011. https://doi.org/10.1515/9783110849455.

MLA (9th ed.) Citation

Fenchel, Werner. Elementary Geometry in Hyperbolic Space. Originally published 1989. De Gruyter, 2011. https://doi.org/10.1515/9783110849455.