Balog, Krisztian ; Azzopardi, Leif ; de Rijke, Maarten: Formal models for expert finding in enterprise corpora. In: SIGIR '06: Proceedings of the 29th annual international ACM SIGIR conference on Research and development in information retrieval. New York, NY, USA : ACM, 2006. - ISBN 1-59593-369-7, S. 43--50