Salmon, R. L., Hutchinson, D. N., Thornton, L., Gray, S., Salmon, R. A., Bingham, P., Hutchinson, D. A., Rowe, B., Newton, D., Syed, Q. U., "The problems of tracing a geographically widespread outbreak of salmonellosis from a commonly eaten food: Salmonella typhimurium DT193 in North West England and North Wales in 1991", Epidemiology and Infection, 1993