Singh, S., U. Mohan, N. Shukla, S. Pandey, S. S. Singh, U. S. Pandey, and S. Tiwari. “Case Control Study of Electrocardiographic Changes in Pregnant Women”. Indian Journal of Community Health, Vol. 8, no. 2,3, Sept. 1995, pp. 24 -27, https://www.iapsmupuk.org/journal/index.php/IJCH/article/view/28.