ThereminVox.Com, Lev Sergeivitch Termen: The Inventor of the Theremin, p. 3. "This apparatus, of which two models existed, one in Cowell’s possession and the other given up by Slonimsky to Schillinger - stirred great arousal in 1932 during an early concert at the New School for Social Research in New York."
Reveillac, Jean-Michel (23 April 2019). Electronic music machines: the new musical instruments. London: John Wiley & Sons. p. 95. ISBN978-1-119-61811-9. OCLC1099434309.