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W.  Niepelt, ?Eine neue Sphingiden-Form?, Internationale Entomologische Zeitschrift, vol. 25, pp. 278-279, 1931.

J. H.  McDunnough, ?A new race of Sphinx gordius (Lepid.)?, Canadian Entomologist, vol. 63, pp. 73-74, 1931.

K.  Jordan, ?On the geographical variation of the Pine Hawkmoth, Hyloicus pinastri?, Novitates Zoologicae, vol. 36, pp. 243-249, 1931.

B.  Gehlen, ?Neue Sphingiden?, Entomologische Zeitschrift, vol. 45, no. 14, pp. 201-204, 1931.

B. P.  Clark, ?Descriptions of seven new Sphingidae and a note on one other?, Proceedings of the New England Zoological Club, vol. 12, pp. 77-83, 1931.

J. D.  Cadbury-3rd, ?A new form of Sphinx gordius (Cramer) (Lepidoptera: Sphingidae)?, Transactions of the American Entomological Society, vol. 57, pp. 319-320, 1931.