↑Purschke, Günter and Jouin, Claude (1988) Anatomy and ultrastructure of the ventral pharyngeal organs of Saccocirrus (Saccocirridae) and Protodriloides (Protodriloidae fam. n.) with remarks on the phylogenetic relationships within Protodrilida (Annelida: Polychaeta). Journal of Zoology, London 215(3): 405-432.