MLA

Morse, William R. (William Reginald), 1874-1939. W. R. Morse (WRM) and Anne Crosse Kinney Morse (ACM) to Mother and Rose en route to China. 1, folder 1. 1909 September-October. https://collections.library.yale.edu/catalog/33391795.

APA, 6th edition

Morse, William R. (William Reginald), 1874-1939. (["1, folder 1"])(1909 September-October)[W. R. Morse (WRM) and Anne Crosse Kinney Morse (ACM) to Mother and Rose en route to China]. https://collections.library.yale.edu/catalog/33391795.