Invasive Species Compendium - Styela clava
Delivering Alien Invasive Species Inventories for Europe: Species Factsheet - Styela clava
European Commission. Sixth Framework Programme.
Non-native Species Information: Leathery Sea Squirt
Great Britain Non-Native Species Secretariat.
Narragansett Bay Research Reserve. Coastal Training Program. Rhode Island Marine & Estuarine Invasive Species Site.
NEANS Panel Online Guide - Club Tunicate
Northeast Aquatic Nuisance Species Panel.
The Exotics Guide: Non-native Marine Species of the North American Pacific Coast (Revised Sep 2011) - Styla clava
San Francisco Estuary Institute; Center for Research on Aquatic Bioinvasions.
NOBANIS: Invasive Alien Species Fact Sheet - Styela clava (2010; PDF | 66 KB)
European Network on Invasive Alien Species.
See also: NOBANIS Fact Sheets for invasive alien species of the European region, covering both animals and plants, as well as microorganisms
Global Invasive Species Database - Styela
IUCN. Species Survival Commission. Invasive Species Specialist Group.
National Exotic Marine and Estuarine Species Information System (NEMESIS) - Styela clava
Smithsonian Institution. Smithsonian Environmental Research Center. Marine Invasions Research Lab.
Squirt (Clubbed Tunicate)
New Zealand Ministry of Agriculture and Forestry. Biosecurity New Zealand.
Sea Squirt (Styela clava) Fact Sheet
National Institute of Water and Atmospheric Research (New Zealand).
Species: Styela clava
Joint Nature Conservation Committee (United Kingdom).
Aquatic Invasive Species: Invasive Tunicate Species Management Program
Washington Department of Fish and Wildlife.
Tunicate Identification Card: Colonial Tunicate
and Club Tunicate (PDF | 1.6 MB)
University of Washington. Washington Sea Grant Program.