MLA

Clay, Black Hills Porcelain, and Marble Mining Company. Prospectus : the Black Hills Porcelain Clay and Marble Mining Company (Incorporated under Laws of South Dakota) ... The Company?, 1900. https://collections.library.yale.edu/catalog/10268369.

APA, 6th edition

Clay, B. H. P., & Company, M. M. (1900). Prospectus : the Black Hills Porcelain Clay and Marble Mining Company (incorporated under laws of South Dakota) ... [Photomechanical prints, Promotional literature, Prospectuses]. The Company?, https://collections.library.yale.edu/catalog/10268369.