Spamer, E.E., comp., 1990, Geology of the Grand Canyon: An annotated bibliography, with an annotated catalogue of Grand Canyon type fossils. v. 4. Third supplement (to 1989), with supplement to the annotated bibliography of the world literature on the Grand Canyon type fossil Chuaria circularis Walcott, 1899: Geological Society of America Microform Publication 20, 178 p.