H. A. Majid and  N. Razali and  M. S. Sulaiman and  A. K. A'ain,  A Capacitive Sensor Interface Circuit Based on Phase Differential Method.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    July 2009, vol. 31(7). 1481 - 1484
    [viewed 21 January 2020]. Available from: https://publications.waset.org/pdf/10448.