Souto, C., C. L. C. Manso, and L. Martins. “Rediscovery and Redescription of Cassidulus Infidus (Echinoidea: Cassidulidae) from Northeastern Brazil”. Zootaxa, vol. 3095, no. 1, Nov. 2011, pp. 39–48, doi:10.11646/zootaxa.3095.1.4.