MLA

Loy, Mina (1882-1966). "Soldier". Box 5, folder 147. n.d.. https://collections.library.yale.edu/catalog/11701062.

APA, 6th edition

Loy, Mina (1882-1966). (["Box 5, folder 147"])(n.d.)["Soldier"]. https://collections.library.yale.edu/catalog/11701062.