MLA

Tolkien, J. R. R. (John Ronald Reuel), 1892-1973. AL to George Gordon. Box 1 | Folder 11. 1927 Aug 3. https://collections.library.yale.edu/catalog/16826351.

APA, 6th edition

Tolkien, J. R. R. (John Ronald Reuel), 1892-1973. (["Box 1 | Folder 11"])(1927 Aug 3)[AL to George Gordon]. https://collections.library.yale.edu/catalog/16826351.