MLA

Ochoa Carrillo, Antonio, 1811-1883. Corona, Ramón. Secretarial letter, signed: Mazatlán, to Antonio Ochoa Carrillo. Box 1, folder 72. 1868 May 21. https://collections.library.yale.edu/catalog/32320203.

APA, 6th edition

Ochoa Carrillo, Antonio, 1811-1883. (["Box 1, folder 72"])(1868 May 21)[Corona, Ramón. Secretarial letter, signed: Mazatlán, to Antonio Ochoa Carrillo]. https://collections.library.yale.edu/catalog/32320203.