VOZNAK, M.; ZBRANEK, I.; MEHIC, M.; KOMOSNY, D.; TORAL-CRUZ, H.; LIN, J. C.-W. Covert Channel in RTP Payload Using a Pointer in Sip Header. Communications - Scientific letters of the University of Zilina, v. 18, n. 1, p. 40-47, 29 Feb. 2016.