"Circulars and Circular Letters"
MLA
Thayer, Scofield, 1889-1982. "Circulars and Circular Letters". Box 12, folder 336. 1920-24, n.d.. https://collections.library.yale.edu/catalog/2044548.
APA, 6th edition
Thayer, Scofield, 1889-1982. (["Box 12, folder 336"])(1920-24, n.d.)["Circulars and Circular Letters"]. https://collections.library.yale.edu/catalog/2044548.