Petrunkevitch 1955. Arachnida. Stormer, L.; Petrunkevitch, A.; Hedgpeth, J.W.Treatise on invertebrate paleontology. Part P. Arthropoda 2. Chelicerata with sections on Pycnogonida and Palaeoisopus., Geological Society of America & University of Kansas Press, Boulder & Lawrence, 1955: 42-173. Chapter pagination: 42-173