@inbook{57836530, author={David M. Vock}, editor={Lopes, Renato D. and Harrington, Robert A.}, title={Chapter 13. Challenges of Observational Designs}, booktitle={Understanding Clinical Research}, publisher={The McGraw-Hill Companies}, address={New York, NY}, year={2013}, url={accessbiomedicalscience.mhmedical.com/content.aspx?aid=57836530} }