Porter, G., Harris, F., Lyon, F., Dung, J., & Adepetu, A. (2003). Markets, ethnicity and environment in a vulnerable landscape: the case of small-scale vegetable production on the Jos Plateau, Nigeria, 1991-2001. The Geographical Journal, 169(4), 370-381. https://doi.org/10.1111/j.0016-7398.2003.00100.x