This document references four sources about crustaceans and freshwater isopods in North America: Hickman et al.'s 2012 animal diversity textbook discusses isopods on pages 245-265; Richardson's 1905 monograph describes North American isopods from pages 409-433; Williams' 1970 paper revises epigean species of the genus Asellus based on specimens from the Smithsonian Institution; Williams' 1972 EPA work provides a guide to freshwater isopods of North America.

18. Hickman, C.P., Roberts, L.S., Keen, S.L., Larson, A.,
Eisenhour, D. J. (2012). Animal Diversity (6th ed., pp.
245–265). New York, NY: McGraw-Hill.
Richardson, H. (1905). A monograph on the isopods of North
America (pp. 409–433). Washington, D.C.: Smithsonian
Institution United States National Museum.
Williams, W. D. (1970). A revision of North American
epigean species of Asellus (Crustacea: Isopoda).
Smithsonian Contributions to Zoology, (49), 1–80.
doi:10.5479/si.00810282.49
Williams, W. D. (1972). Freshwater Isopods (Asellidae) of North
America. Washington, D.C.: U.S. Enviromental Protection
Agency.