Richard Sewall Hunter: Photoelectric Color-Difference Meter. In: JOSA. 38. Jahrgang, Nr.7, Juli 1948, S.661 (opticsinfobase.org). (Proceedings of the Winter Meeting of the Optical Society of America)
Richard Sewall Hunter: Accuracy, Precision, and Stability of New Photo-electric Color-Difference Meter. In: JOSA. 38. Jahrgang, Nr.12, Dezember 1948, S.1094 (opticsinfobase.org). (Proceedings of the Thirty-Third Annual Meeting of the Optical Society of America).
