Alexander Karp is a professor of mathematics education at Teachers College, Columbia University. He received his Ph.D. in mathematics education from Herzen Pedagogical University in St. Petersburg, Russia, and also holds a degree from the same university in history and education. Currently, his scholarly interests span several areas, including the history of mathematics education, gifted education, mathematics teacher education, and the theory of mathematical problem solving. He is the managing editor of the International Journal for the History of Mathematics Education and the author of over one hundred publications, including over twenty books. Gert Schubring is a retired member of the Institut für Didaktik der Mathematik, a research institute at Bielefeld University, and at present is visiting professor at the Universidade Federal do Rio de Janeiro (Brazil). His research interests focus on the history of mathematics and the sciences in the eighteenth and nineteenth centuries and their systemic interrelation with social-cultural systems. One of his specializations is history of mathematics education. He has published several books, among which is Conflicts between Generalization, Rigor and Intuition: Number Concepts Underlying the Development of Analysis in 17th–19th Century France and Germany (New York, 2005). He is Chief-Editor of the International Journal for the History of Mathematics Education.