Cite

Undated (letter fragments and notes)

MLA

Yale Peruvian Expedition ($d: 1911). Undated (letter fragments and notes). Box 13, folder 209. Undated (letter fragments and notes). https://collections.library.yale.edu/catalog/33346360.

APA, 6th edition

Yale Peruvian Expedition ($d: 1911). (["Box 13, folder 209"])(Undated (letter fragments and notes))[Undated (letter fragments and notes)]. https://collections.library.yale.edu/catalog/33346360.