MLA

Morse, William R. (William Reginald), 1874-1939. WRM to Mother from Yachow, Chengtu (Chengdu), boat on Chengtu River. 1, folder 16. 1911 February. https://collections.library.yale.edu/catalog/33542366.

APA, 6th edition

Morse, William R. (William Reginald), 1874-1939. (["1, folder 16"])(1911 February)[WRM to Mother from Yachow, Chengtu (Chengdu), boat on Chengtu River]. https://collections.library.yale.edu/catalog/33542366.