M. Bello, Musa, et al. “Challenges of Immunization Coverage Among a Semi-Nomadic Population in Kano State, North West Nigeria”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 27, no. 3, June 2016, pp. 186-93, https://www.gssrr.org/JournalOfBasicAndApplied/article/view/4503.