Rohil, V., V. Vijayan, R. Kumar, R. Joshi, P. Pavani, S. Paul, A. Sharma, and M. Rahman. “A Study on the Correlation of Matrix Metalloproteinase MMP1 in COPD and Smoking in the North Indian Population”. Asian Journal of Medical Sciences, Vol. 8, no. 1, Jan. 2017, pp. 5-14, doi:10.3126/ajms.v8i1.16020.