Yousif, H.M. <https://pure.iiasa.ac.at/view/iiasa/1674.html> ORCID: https://orcid.org/0000-0001-8071-1395 <https://orcid.org/0000-0001-8071-1395>  (1995).  Population, biomass and the environment in central Sudan.   International Journal of Sustainable Development and World Ecology 2 (1) 54-69. 10.1080/13504509509469889 <https://doi.org/10.1080/13504509509469889>.