MLA

[Sketchbook]. 0AD. https://collections.library.yale.edu/catalog/11236916.

APA, 6th edition

[Sketchbook]. (0 C.E.). [Graphite drawings--United States--20th century.--gmgpc, Ink drawings.--gmgpc, Landscape drawings, Portrait drawings, Silver points (AAT), Sketches--United States--20th century.--aat]. https://collections.library.yale.edu/catalog/11236916.