http://www.conchology.uunethost.be/GENERAL/Cyberconchology/SuperConch/Gastropoda/HYDATINIDAE.html
http://www.seaslugforum.net/factsheet.cfm?base=hydazona
http://www.umiushi.info/photo_species/photo_splist_eng.php?sopt=0&loc=0000
http://www.ne.jp/asahi/kappa-kuri/miyamoto/OSEHOO/umiushi220.html
http://www.medslugs.de/E/Pac-NW/Hydatina_zonata.htm
http://www.Philippine-Sea-Slugs.com/CEPHALASPIDEA/Hydatina_zonata.htm