@article{Valderas2009,
author = {Valderas, J.M. and Starfield, B. and Sibbald, B. and Salisbury, C. and Roland, M.},
title= {Defining comorbidity: Implications for understanding health and health services},
year = {2009},
doi = {10.1370/afm.983},
volume = {7},
number = {4},
pages = {357‒363},
}