Md. Nasimuzzaman Chowdhury, and Md. Khaled Hossain. “M2M: GSM Network for Robots Using DTMF”. Global Journals of Research in Engineering 13, no. F10 (July 15, 2013): 23–29. Accessed May 5, 2024. https://engineeringresearch.org/index.php/GJRE/article/view/863.