MLA

Mondrian, Piet, 1872-1944. Autograph letter, signed, from Cornelis van Eesteren, also signed by fourteen architects and designers. Box 4, folder 93. 1932 Feb 29. https://collections.library.yale.edu/catalog/16626956.

APA, 6th edition

Mondrian, Piet, 1872-1944. (["Box 4, folder 93"])(1932 Feb 29)[Autograph letter, signed, from Cornelis van Eesteren, also signed by fourteen architects and designers]. https://collections.library.yale.edu/catalog/16626956.