MLA

Yung, Wing, 1828-1912. Schwab, John Christopher. Box 1, folder 6 | reel 1U. 1909. https://collections.library.yale.edu/catalog/10013178.

APA, 6th edition

Yung, Wing, 1828-1912. (["Box 1, folder 6 | reel 1U"])(1909)[Schwab, John Christopher]. https://collections.library.yale.edu/catalog/10013178.