1. Campbell, P. Nature 324, 523–528 (1986).
2. Schroeder, M.R. Number Theory in Science and Communication. With Applications in Cryptography, Physics, Digital Information, Computing and Self-Similarity 2nd edn Ch. 30 (Springer, New York 1986).
3. Risset, J.C. Proc. 7th Int. Conf. Acoust., Budapest, Vol. 3, 613–616 (Akadémiai-Kiadó, Budapest, 1971).
4. Charbonneau, G. & Risset, J.-C. C. r. hebd. Séane. Acad. Sci., Paris B281, 289–292 (1975).
5. Schroeder, M.R. J. acoust. Soc. Am. 79, 186–189 (1986).