Swen, H. M., and Wolthers, B. G. (1968). "Structure of papain". Nature, 218:929-932. Dyson, H. J., Sayre, J. R., Merutka, G., Shin, H. C., Lerner, R. A
Jason A. (2019-01-01). “Miniaturisation in Chelicerata” (英語). Arthropod Structure & Development 48: 20–34. doi:10.1016/j.asd.2018.10.002. ISSN 1467-8039