Zieleniewski, M.; Brent, A. Evaluating the Costs and Achievable Benefits of Extending Technologies for Uneconomical Coal Resources in South Africa: The Case of Underground Coal Gasification. J. energy South. Afr. 2008, 19 (4), 21-31. https://doi.org/10.17159/2413-3051/2008/v19i4a3335.