Mohamed T. Elhadi Wojciech Ziarko A Rough Sets Approach to the Identification and Analysis of Factors Affecting Biological Control of Leafy Spurge. 75-92 2008 8 T. Rough Sets http://dx.doi.org/10.1007/978-3-540-85064-9_5 journals/trs/2008-8 db/journals/trs/trs8.html#ElhadiZ08