R. Korfhage. SIGIR '85: Proceedings of the 8th annual international ACM SIGIR conference on Research and development in information retrieval, page 33--40. New York, NY, USA, ACM, (1985)
P. Soffer, and I. Hadar. Eighth CAiSE/IFIP8.1 International Workshop on Evaluation of Modeling Methods in Systems Analysis and Design (EMMSAD'03), page 126-134. (2003)
M. Nurminen, and J. Itkonen. Concept Mapping - Connecting Educators. Proceedings of the 3rd International Conference on Concept Mapping. Volume III. Poster papers, page 202-205. IHMC, (2008)