Federal Communications Commission (2003). Communications Regulation. Vol. 28. Silver Springs, MD: Pike & Fischer, Inc. p. 680. Retrieved 24 February 2016.
Kalahasty, G.; Alimohammed, R.; Mahajan, R.; Morjaria, S.; Ellenbogen, K.A. (2013). "A Brief History of Remote Cardiac Monitoring". In Asirvatham, S.J.; Venkatachalam, K.L.; Kapa, S. (eds.). Remote Monitoring and Physiologic Sensing Technologies and Applications. Philadelphia, PA: Elsevier, Inc. pp. 275–282. ISBN9780323188463. Retrieved 24 February 2016.