Hansell, A., Hollowell, J., Nichols, T., McNiece, R., & Strachan, D. (1999). Use of the General Practice Research Database (GPRD) for respiratory epidemiology: a comparison with the 4th Morbidity Survey in General Practice (MSGP4). Thorax.
Soriano, J. B., Kiri, V. A., Maier, W. C., & Strachan, D. (2003). Increasing prevalence of asthma in UK primary care during the 1990s. Int J Tuberc Lung Dis.