Parent Horacio, Taxonomic and biostratigraphic re-evaluation of Perisphinctes internispinosus KRANTZ, 1926 (Upper Jurassic, Ammonoidea), Palaontologische Zeitschrift Palaontologische Zeitschrift (Print);Journal of Palaontologische Gesellschaft Scientific contributions to palaeontology, 77(2), 2003, pp. 353-360