Vacelet, Jean, Philippe Willenz, and Willard Hartman. “Treatise Online, No. 1, Part E, Revised, Volume 4, Chapter 1: Living Hypercalcified Sponges”. Treatise Online (January 18, 2011). Accessed May 18, 2024. https://journals.ku.edu/treatiseonline/article/view/4069.