Ali, Jawad, et al. “Cloud Based Multi-Level Security, Event Based Surveillance and Real-Time Access in Smart Homes Using Zigbee: Real-Time Access in Smart Homes Using Zigbee”. Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, vol. 57, no. 4, Aug. 2021, pp. 13-22, http://ppaspk.org/index.php/PPAS-A/article/view/449.