1. Curt Sachs, The History of Musical Instruments, c2006, Dover Edition, originally published in 1940 by W.W. Norton, NY.
2. https://commons.wikimedia.org/wiki/File:SlitDrum,Cameroon,Br%C3%BCcke-MuseumBerlin,65053,viewa.jpg
3. Complete Set of Gamelan Orchestra Instruments web site: https://factsofindonesia.com/gamelan-orchestra-instruments
4. Donald E. Hall, Musical Acoustics, c 2002, Brooks/Cole, Pacific Grove, CA.
5. Randy Warland, J Acoust Soc Am., Jan;127(1):525-33 (2010). https://doi.org/10.1121/1.3268605.