Cardiocarpon spinatus (megaspore membrane gametophyte tissue?), Box: 2, item: 5, Page: 100. Study of the Middle Pennsylvanian Flora Found in Kansas Coal Balls, RH MS 1259. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/57696 Accessed July 15, 2025.