Williams, Alwyn, D. V. Ager, R. E. Grant, A. J. Rowell, F. G. Stehli, H. M. Muir-Wood, and G. F. Elliott. “Part H, Brachiopoda, Vol. 1 & 2, Ch. 1, P. 1-157”. Treatise on Invertebrate Paleontology (January 1, 1965). Accessed May 2, 2024. https://journals.ku.edu/InvertebratePaleo/article/view/5543.