R. Hasan, A. Zafar, Z. Abbas, V. Mahraj, F. Malik, and A. Zaidi, “Antibiotic resistance among Salmonella enterica serovars Typhi and Paratyphi A in Pakistan (2001-2006)”, J Infect Dev Ctries, vol. 2, no. 04, pp. 289–294, Aug. 2008.