MLA

Gibbs, J. Willard (Josiah Willard), 1839-1903. Freeman, Alexander - 8 autograph letters, signed, to Josiah Willard Gibbs.. Box 2, folder 64. 1875-1890. https://collections.library.yale.edu/catalog/2013216.

APA, 6th edition

Gibbs, J. Willard (Josiah Willard), 1839-1903. (["Box 2, folder 64"])(1875-1890)[Freeman, Alexander - 8 autograph letters, signed, to Josiah Willard Gibbs.]. https://collections.library.yale.edu/catalog/2013216.