MLA

England, and Wales. Post Office. Penny-Post-Office, Westminster. publisher not identified, 0AD. https://collections.library.yale.edu/catalog/16871548.

APA, 6th edition

E., & Office, W. P. (0 C.E.). Penny-post-office, Westminster [Ephemera, Annotations (Provenance) 18th century]. publisher not identified. https://collections.library.yale.edu/catalog/16871548.