Cite

Undated (letters)

MLA

Yale Peruvian Expedition ($d: 1911). Undated (letters). Box 13, folder 208. Undated (letters). https://collections.library.yale.edu/catalog/33346327.

APA, 6th edition

Yale Peruvian Expedition ($d: 1911). (["Box 13, folder 208"])(Undated (letters))[Undated (letters)]. https://collections.library.yale.edu/catalog/33346327.