MLA

Grinnell, Julius S. (Julius Sprague), 1842-1898. Klaessig, Emil. Box 2, folder 34. [18]84 Feb 6. https://collections.library.yale.edu/catalog/2112508.

APA, 6th edition

Grinnell, Julius S. (Julius Sprague), 1842-1898. (["Box 2, folder 34"])([18]84 Feb 6)[Klaessig, Emil]. https://collections.library.yale.edu/catalog/2112508.