{{cite book | last = Gibson | first = R. H. | author2 = Maurice Prendergast | title = The German Submarine War, 1914–1918 | location = Annapolis, Maryland | publisher = Naval Institute Press | year = 2003 | orig-year = 1931 | isbn = 9781591143147 | oclc = 52924732 | page = {{{page|}}} | pages = {{{pages|}}} }}