Helwerda, R. A., F. P. Wesselingh, and S. T. Williams. “On Some Vetigastropoda (Mollusca, Gastropoda) from the Plio-Pleistocene of the Philippines With Descriptions of Three New Species”. Zootaxa, vol. 3755, no. 2, Jan. 2014, pp. 101–135, doi:10.11646/zootaxa.3755.2.1.