O. Etzioni, M. Cafarella, D. Downey, A.M. Popescu, T. Shaked, S. Soderland, D.S. Weld, und A. Yates. Unsupervised named-entity extraction from the web: An experimental study. Artificial Intelligence, (165)1:91--134, Elsevier Science Publishers Ltd. Essex, UK, 2005. [PUMA: ie unsupervised learning ml] URL