Ritchie, Alexander (1985). "Ainiktozoon loganense Scourfield, a protochordate? from the Silurian of Scotland". Alcheringa. 9 (2): 137. doi:10.1080/03115518508618961.
Mayer, G. (2006). "Structure and development of onychophoran eyes: What is the ancestral visual organ in arthropods?". Arthropod Structure and Development. 35 (4): 231–245. doi:10.1016/j.asd.2006.06.003. PMID18089073.
Mayer, G. (2006). "Structure and development of onychophoran eyes: What is the ancestral visual organ in arthropods?". Arthropod Structure and Development. 35 (4): 231–245. doi:10.1016/j.asd.2006.06.003. PMID18089073.