The goal of this paper is to develop methods to handle inconsistent knowledge elicited from multiple sources. Knowledge is represented using predicates that define relationships within three sets: domain objects, concepts, and knowledge sources. Sources express their comprehension of the use of each concept to describe each object by giving their votes: yes, no, and no-op. We also derive and interpret internal relations between any pair of subsets of the same type taken of the three sets: objects, concepts, and sources. We refer to the relations between any two subsets of different types as external relations. Intersections between the sets are interpreted as multilevel structures of knowledge and they are used for knowledge refinement. The refinement technique presented is based on the derivation of the most supported opinion of the group of experts and refining it further using a multilevel structure of knowledge sources.