“Automatic College Bell Using Raspberry-Pi”, Int. J. Emerg. Trends Sci. Technol., vol. 3, no. 06, pp. 4086–4089, Jun. 2016, Accessed: Sep. 28, 2026. [Online]. Available: http://igmpublication.com/ijetst.in/index.php/ijetst/article/view/1091