MLA

Pratt, Richard Henry, 1840-1924. Stevick, Guy LeRoy, 10 items. Box 18, folder 623. 1903-19. https://collections.library.yale.edu/catalog/17104188.

APA, 6th edition

Pratt, Richard Henry, 1840-1924. (["Box 18, folder 623"])(1903-19)[Stevick, Guy LeRoy, 10 items]. https://collections.library.yale.edu/catalog/17104188.