@inbook{57836443,
author={Bradley G. Hammill},
editor={Lopes, Renato D. and Harrington, Robert A.},
title={Chapter 12. Observational Study Designs},
booktitle={Understanding Clinical Research},
publisher={The McGraw-Hill Companies},
address={New York, NY},
year={2013},
url={accessbiomedicalscience.mhmedical.com/content.aspx?aid=57836443}
}