Frith, P., Attewell, R., Crockett, A., Price, D., & Beilby, J. (2006). ABS49: Splitting COPD and asthma: Validation of the differential diagnosis questionnaire (DDQ) in Australian primary care. Prim Care Respir J.

Frith, P., R. Attewell, A. Crockett, D. Price, και J. Beilby. "ABS49: Splitting COPD and Asthma: Validation of the Differential Diagnosis Questionnaire (DDQ) in Australian Primary Care." Prim Care Respir J 2006.

Frith, P., et al. "ABS49: Splitting COPD and Asthma: Validation of the Differential Diagnosis Questionnaire (DDQ) in Australian Primary Care." Prim Care Respir J 2006.