MLA

Bischoff, Ferdinand R, Ecker, Alexander, 1816-1887. Embryonic development. Undated. https://collections.library.yale.edu/catalog/2036677.

APA, 6th edition

Bischoff, Ferdinand R, & Ecker, Alexander, 1816-1887. (Undated)[Embryonic development]. https://collections.library.yale.edu/catalog/2036677.