MLA

Gibbs, J. Willard (Josiah Willard), 1839-1903. Brunhes, Bernard - 2 autograph letters, signed, to Josiah Willard Gibbs. France.. Box 2, folder 40. 1902 October 26 and November 14. https://collections.library.yale.edu/catalog/17296912.

APA, 6th edition

Gibbs, J. Willard (Josiah Willard), 1839-1903. (["Box 2, folder 40"])(1902 October 26 and November 14)[Brunhes, Bernard - 2 autograph letters, signed, to Josiah Willard Gibbs. France.]. https://collections.library.yale.edu/catalog/17296912.