@article{doi:10.2106/JBJS.H.01571,
author = {Hoppe, Daniel J. and Schemitsch, Emil H. and Morshed, Saam and TornettaIII, Paul and Bhandari, Mohit},
title = {Hierarchy of Evidence: Where Observational Studies Fit in and Why We Need Them},
journal = {The Journal of Bone & Joint Surgery},
volume = {91},
number = {Supplement_3},
pages = {2-9},
year = {2009},
doi = {10.2106/JBJS.H.01571},
URL = { + http://dx.doi.org/10.2106/JBJS.H.01571},
eprint = {}
}