Faulkner, Virginia.  "A Guide to Rotograph Cards."  The Rotograph Review 1.1 (Winter 1977): 2-5.

Geary, Christraud M., and Webb, Virginia-Lee, eds.  Delivering Views: Distant Cultures in Early Postcards.  Washington, DC: Smithsonian Institution, 1998.

Lowe,  James Lewis.  "The Rotograph Company of New   York."  Postcard Classics, no. 10 , n.d. : 145, 149-150, and 163-164.  Not dated in my copy, but published some time after the first issues of the 1977 Rotograph Review, to which it refers.

The Rotograph Review (1977).