Cite

Symbolproblem: research notes (Envelope #31)

MLA

Cassirer, Ernst, 1874-1945. Symbolproblem: research notes (Envelope #31). Box 51, folder 1025. n.d.. https://collections.library.yale.edu/catalog/17274647.

APA, 6th edition

Cassirer, Ernst, 1874-1945. (["Box 51, folder 1025"])(n.d.)[Symbolproblem: research notes (Envelope #31)]. https://collections.library.yale.edu/catalog/17274647.