Pant, P, B Yadav, GM Khan, R Koju, R Gurung, B Pokharel, TRS Bedi, and RK Adkhari. 2011. “Role of Tiotropium in Chronic Obstructive Pulmonary Disease Exacerbation”. Journal of Institute of Medicine Nepal 32 (2):5-10. https://www.nepjol.info/index.php/JIOM/article/view/4937.