2 literature references for Phorbas perarmatus (Bowerbank, 1866):

Author: Van Soest, R.W.M.
Year: 2001
Title: Porifera, in: Costello, M.J. et al. (Ed.) (2001).
Source: European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50:
Author: Bowerbank, J.S.
Year: 1866
Title: A Monograph of the British Spongiadae. Volume 2. (
Source: Ray Society: London): i-xx, 1-388.