MLA

Lindbergh, Charles A. (Charles Augustus), 1902-1974. Chaco Canyon, New Mexico. Box 8, folder 31. 1929 July. https://collections.library.yale.edu/catalog/10013243.

APA, 6th edition

Lindbergh, Charles A. (Charles Augustus), 1902-1974. (["Box 8, folder 31"])(1929 July)[Chaco Canyon, New Mexico]. https://collections.library.yale.edu/catalog/10013243.