VLADIMIR ANGULO CASTILLO, ELDER JESUS VILLAMIZAR ROA, YURILEV CHALCO CANO, En: Colombia - Fuzzy Sets and Systems ISSN: 0165-0114 ed: Elsevier Science Bv v.265 fasc. p.24 - 38 ,2015, DOI: doi.org/10.1016/j.fss.2014.07.015