1. Gardiner G. Hubbard: The Story of the Rise of the Oral Method in America. Volta Bureau, Washington. 49 S. 1898 / 2. Joseph C. Gordon: The Difference between the two Systems of Teaching deaf-mute children the English language. Volta Bureau. Suppl. Elucid. Circul. of Inform. (4). Washington 1898
Heller, Th..
1900.
1. Gardiner G. Hubbard: The Story of the Rise of the Oral Method in America. Volta Bureau, Washington. 49 S. 1898 / 2. Joseph C. Gordon: The Difference between the two Systems of Teaching deaf-mute children the English language. Volta Bureau. Suppl. Elucid. Circul. of Inform. (4). Washington 1898.
In: Zeitschrift für Psychologie und Physiologie der Sinnesorgane 22: 313-314.