The Cephalopoda of the Plankton Expedition / G. Pfeffer ; scientific editor, Sigurd v. Boletzky ; general editor, Clyde F.E. Roper ; foreword to this edition Clyde F.E. Roper ; [translator Indira Kohli]. (Results of the Plankton Expedition of the Humboldt Foundation ; vol. 2 F. a)
The Cephalopoda of the Plankton Expedition / G. Pfeffer ; scientific editor, Sigurd v. Boletzky ; general editor, Clyde F.E. Roper ; foreword to this edition Clyde F.E. Roper ; [translator Indira Kohli].
(Results of the Plankton Expedition of the Humboldt Foundation ; vol. 2 F. a)