D. M. Bansal, D. M. Goyal, D. J. K. Dhillon, and D. P. Kaur, “Longitudinal Study Of Peak Expiratory Flow Rate In Pregnant Women: Study of Peak Expiratory Flow Rate in Pregnant Women”, Natl J Integr Res Med, vol. 3, no. 1, pp. 34–38, Mar. 2012.