Using Fuzzy Sets in Surgical Treatment Selection and Homogenizing Stratification of Patients with Significant Chronic Ischemic Mitral Regurgitation. - Natalia D. Nikolova; Plamen Panayotov; Daniela Panayotova; Snejana D. Ivanova; Kiril Tenekedjiev (Int. J. Comput. Intell. Syst., 2019)