1. Department of Information Science, University of Pretoria, IT-building 6-72, Pretoria , South Africa
2. Department of African Languages, University of Pretoria, GW/HB 2-14, Pretoria , South Africa
3. Institut für Informationswissenschaft und Sprachtechnologie, Universität Hildesheim, Universitätsplatz 1, 31141 Hildesheim , Germany