MLA

Carson, Rachel, 1907-1964. Nickell, Walter. Box 43, folder 815. 1958-59. https://collections.library.yale.edu/catalog/17145178.

APA, 6th edition

Carson, Rachel, 1907-1964. (["Box 43, folder 815"])(1958-59)[Nickell, Walter]. https://collections.library.yale.edu/catalog/17145178.