MLA

Wallis, B. C. (Bertie Cotterell), cartographer. Hungary, nationalities. [1918]. https://collections.library.yale.edu/catalog/15238054.

APA, 6th edition

Wallis, B. C. (Bertie Cotterell), cartographer. ([1918])[Hungary, nationalities]. https://collections.library.yale.edu/catalog/15238054.