Bull, Michael. “Williams, Andrew. 2007. ’Portable Music and Its Functions’. New York: Peter Lang. ISBN 978-0-8204-8125-8 (pbk). 127 Pp”. Perfect Beat 10, no. 2 (November 11, 2009): 223–224. Accessed June 7, 2024. https://journal.equinoxpub.com/PB/article/view/16557.