Chaudhry, J. A., F. A. Khan, and M. M. Pervaiz. “APMP INTERCOMPARISON OF DC VOLTAGE STANDARD AT NPSL ISLAMABAD”. Biological Sciences - PJSIR, vol. 45, no. 2, Apr. 2002, pp. 140-4, https://v2.pjsir.org/index.php/biological-sciences/article/view/1773.