“U.S. Naval Observatory, Washington. Auxiliary apparatus, consisting of motor-generator with adjustable speed control and phase shifter, which supplies current for the synchronous motor”, circa 1933, Bibliothèque de l'Observatoire de Paris, inv.I.887. Consulté le 25 avr. 2024, https://bibnum.explore.psl.eu/s/psl/ark:/18469/1gp9s
