Bernd Heine is Emeritus Professor of Linguistics at the Institute of African Studies, University of Cologne. His 33 books include Auxiliaries: Cognitive forces and grammaticalization (OUP USA, 1993); Cognitive Foundations of Grammar (OUP USA, 1997); Possession: Cognitive sources, forces, and grammaticalization (CUP, 1997); and, with Derek Nurse, African Languages: An introduction (CUP, 2000). Tania Kuteva is Professor of English Language and Linguistics at the University of Dusseldorf and author of Auxiliation: An enquiry into the nature of grammaticalization (OUP, 2001). Bernd Heine and Tania Kuteva are the joint authors of World Lexicon of Grammaticalization (CUP, 2002) and Language Contact and Grammatical Change (CUP, 2005).