Underground comix changed the economics of comic book publishing in the 1970s. Underground Classics: The Transformation of Comics into Comix2 provides the history of the change from comics to comix.
Solondz, Simone (2021). Underground Comix Meet the Fleet. Rhode Island School of Design News. (7/13).
Danky, James Philip, Denis Kitchen, and Jay. Lynch. Underground Classics : the Transformation of Comics into Comix . New York: Abrams, 2009.
Underground Comix collection, 1948-1978. Division of Rare and Manuscript Collections
Cornell University Library.
New Resources: Underground and Independent Comics, Comix, and Graphic Novels (Digital Collection) (2019). University of California Berkeley. (9/5).
Guide to the Lynn R. Hansen Underground Comics Collection 1899-1994. Washington State University, Libraries Manuscripts, Archives, and Special Collections.