MLA

Purdy, Richard Little, 1904-1990. "The Dorset Farm Labourer," rough proof, corrected. Box 1, folder 19. 1856-1966. https://collections.library.yale.edu/catalog/2012196.

APA, 6th edition

Purdy, Richard Little, 1904-1990. (["Box 1, folder 19"])(1856-1966)["The Dorset Farm Labourer," rough proof, corrected]. https://collections.library.yale.edu/catalog/2012196.