SCHÖNHOFEN, Péter; CHARAF, Hassan. Document Retrieval through Concept Hierarchy Formulation. Periodica Polytechnica Electrical Engineering, [S. l.], v. 45, n. 2, p. 91–108, 2001. Disponível em: https://pp.bme.hu/ee/article/view/978. Acesso em: 3 may. 2024.