R.M.W. Dixon is Professor and Director of the Research Centre for Linguistic Typology at La Trobe University. He has published grammars of a number of Australian languages (including Dyirbal and Yidin), in addition to A Grammar of Boumaa Fijian (University of Chicago Press 1988), A New Approach to English Grammar, on Semantic Principles (OUP 1991, revised edition in preparation), and The Jarawara Language of Southern Amazonia (OUP 2004). His books on typological theory include Where have all the Adjectives Gone? and other Essays in Semantics and Syntax (1982) and Ergativity (1994). His essay The Rise and Fall of Languages (1997) expounded a punctuated equilibrium model for language development which is the basis for his detailed case study Australian Languages: their Nature and Development (2002). He is currently working on an extensive study of basic linguistic theory. Alexandra Y. Aikhenvald is Professor and Associate Director of the Research Centre for Linguistic Typology at La Trobe University. She has worked on descriptive and historical aspects of Berber languages and has published in Russian a grammar of Modern Hebrew (1990). She is a major authority on languages of the Arawak family of northern Amazonia, and has written grammars of Bare (1995, based on work with the last speaker who has since died) and Warekena (1998), plus A Grammar of Tariana, from Northwest Amazonia (CUP 2003). Her books include Classifiers: a Typology of Noun Categorization devices (OUP 2000, paperback reissue 2003), Language contact in Amazonia (OUP 2002), and Evidentiality (OUP 2004). She is currently working on grammatical description of Manambu, from the Sepik region of New Guinea.