S, V., R. N, and R. B. “A Comparative Study of Safety and Efficacy of Tiotropium Bromide With Salbutamol in Moderate Persistent Bronchial Asthma in a Tertiary Care Hospital”. International Journal of Research in Medical Sciences, vol. 2, no. 4, Jan. 2017, pp. 1479-82, https://www.msjonline.org/index.php/ijrms/article/view/2444.