MLA

Saarinen, Eero, 1910-1961. TWA Proposed Terminal Building, New York International Airport, Eero Saarinen and Associates [includes two different covers]. Box 699, folder 208. undated. https://collections.library.yale.edu/catalog/10187084.

APA, 6th edition

Saarinen, Eero, 1910-1961. (["Box 699, folder 208"])(undated)[TWA Proposed Terminal Building, New York International Airport, Eero Saarinen and Associates [includes two different covers]]. https://collections.library.yale.edu/catalog/10187084.