MLA

Meserve, Frederick Hill, 1865-1962. 565.Battle-field of Gettysburg - Soldiers' Orphans' Home, occupied during the battle as the Headquarters of Gen. O. O. Howard.. Box 78, folder 1138. approximately 1870. https://collections.library.yale.edu/catalog/33399017.

APA, 6th edition

Meserve, Frederick Hill, 1865-1962. (["Box 78, folder 1138"])(approximately 1870)[565.Battle-field of Gettysburg - Soldiers' Orphans' Home, occupied during the battle as the Headquarters of Gen. O. O. Howard.]. https://collections.library.yale.edu/catalog/33399017.