@article {1810, title = {Three sibling species species of didemnid ascidians from northern Norway: Didemnum albidum (Verrill, 1871), Didemnum polare (Hartmeyer, 1903), and Didemnum romssae sp. nov.}, journal = {Canadian Journal of Zoology}, volume = {74}, year = {1996}, pages = {357-379}, author = {Marks, J.A.} }