Randomized, Controlled Trials, Observational Studies, and the Hierarchy of Research Designs.
Concato, John; Shah, Nirav; Horwitz, Ralph I.; New England Journal of Medicine, 2000, vol. 342, issue 25, p 1887, ISSN 00284793. ISBN 00284793.

Full Text Resources Located for this Citation

View article on EBSCOhost(Login required)
View article via CrossRef