Kirkpatrick, P.A.; Pugh, P.R. (1984). Siphonophores and velellids: keys and notes for the identification of the species. <i>Synopses of the British fauna (new series)</i>, 29. E.J. Brill/W. Backhuys: London, UK. ISBN 90-04-07470-8. vi, 154 pp. (look up in IMIS) [details]