@article{Charlson1987,
author = {Charlson, M.E. and Pompei, P. and Ales, K.L. and MacKenzie, C.R.},
title= {A new method of classifying prognostic comorbidity in longitudinal studies: development and validation},
year = {1987},
doi = {10.1016/0021-9681(87)90171-8},
journal = {Journal of Chronic Diseases},
volume = {40},
number = {5},
pages = {373--83},
}