Nerida Ellerton has been a Professor in the Mathematics Department at Illinois State University since 2002. Between 1997 and 2002 she was Professor and Dean of Education at the University of Southern Queensland and, between 1993 and 1997, Professor of Education at Edith Cowan University (1993-1997). Before that, she was Associate Professor at Deakin University, where, in 1991 and 1992, she was Director of the National Centre for Research and Development in Mathematics Education. Nerida holds two PhDs-the first is in Physical Chemistry (from the University of Adelaide), and the second in Mathematics Education (from Victoria University, Wellington). Nerida has written or edited 14 books. She has taught in schools, has served as an international consultant, and has had over 100 refereed scholarly papers published in the fields of mathematics education and chemistry. Between 1993 and 1997 she was editor of the Mathematics Education Research Journal and she is currently Associate Editor for Journal for Research in Mathematics Education. M. A. ("Ken") Clements is a Professor in the Mathematics Department at Illinois State University. After teaching in schools, Ken completed his PhD at the University of Melbourne. He then taught in three Australian universities (Monash, Deakin, and Newcastle), and at Universiti Brunei Darussalam (1997-2004). In 1980 he was a visiting fellow at Cambridge University, and he has served as a consultant in India, Malaysia, PNG, South Africa, Thailand, the United Kingdom, and Vietnam. Ken has co-edited two international handbooks on mathematics education (1996 and 2003) and is editor for Springer's third international handbook. He has written or edited 24 books and more than 200 articles. With Nerida Ellerton, he co-authored a UNESCO book on mathematics education research. Ken is honorary life member of both the Mathematical Association of Victoria and the Mathematics Education Research Group of Australasia.