MLA

Parker, Peter, 1804-1888. William L. Marcy, US Secretary of State to the Emperor of China, letter in Chinese. 1, folder 23. 1855 September 5. https://collections.library.yale.edu/catalog/16808700.

APA, 6th edition

Parker, Peter, 1804-1888. (["1, folder 23"])(1855 September 5)[William L. Marcy, US Secretary of State to the Emperor of China, letter in Chinese]. https://collections.library.yale.edu/catalog/16808700.