MLA

Blanchecotte, A. M. (Augustine Malvine), 1830-1878. "A Lamartine". GROUP 28, folder F-1. 1878 Aug 18. https://collections.library.yale.edu/catalog/10189941.

APA, 6th edition

Blanchecotte, A. M. (Augustine Malvine), 1830-1878. (["GROUP 28, folder F-1"])(1878 Aug 18)["A Lamartine"]. https://collections.library.yale.edu/catalog/10189941.