Eva Thanheiser, Mathematics and Statistics faculty, presented two papers and chaired a working group at the 31st annual meeting of The North American Chapter of the International Group for the Psychology of Mathematics Education, held in Atlanta, Sept. 23-26. The co-authored papers, which will be published in the conference proceedings, are "Exploring Preservice Teachers' Conceptions of Numbers Via the Mayan Number System" and "Understanding Base Ten Numbers: Why Don't You Just Tell Them it is Ten?" The working group was on preservice elementary school teachers' content knowledge in mathematics.