Levy, M. L., Fletcher, M., Price, D. B., Hausend, T., Halbert, R. J., & Yawn, B. P. (2006). International Primary Care Respiratory Group (IPCRG) Guidelines: Diagnosis of respiratory diseases in primary care. Prim Care Respir J.

Levy, Mark L., Monica Fletcher, David B. Price, Thomas Hausend, Ron J. Halbert, e Barbara P. Yawn. "International Primary Care Respiratory Group (IPCRG) Guidelines: Diagnosis of Respiratory Diseases in Primary Care." Prim Care Respir J 2006.

Levy, Mark L., et al. "International Primary Care Respiratory Group (IPCRG) Guidelines: Diagnosis of Respiratory Diseases in Primary Care." Prim Care Respir J 2006.