North-West European thecate hydroids and their medusae : keys and notes for identification of the species /
Cornelius, Paul F. S.
Field Studies Council (Great Britain)
Linnean Society of London.
Estuarine and Coastal Sciences Association.
Shrewsbury : Published for  the        Linnean Society of London and the  Estuarine and Coastal Services Association by Field Studies Council,
1995.
pt. 1. Laodiceidae to Haleciidae -- pt. 2. Sertulariidae to Campanulariidae.