Gwendolyn M. Lloyd is Hermanowicz Professor of Teacher Education and Professor of Mathematics Education at Pennsylvania State University, United States. She serves as Director of Graduate Studies, Curriculum and Instruction, and as Associate Editor of the Review of Educational Research.Olive Chapman is Professor of Mathematics Education at the University of Calgary, Canada. She served as editor-in-chief of the Journal of Mathematics Teacher Education and a member of the Board of Directors of the National Council of Teachers of Mathematics.