Links
Institute of Education Sciences, US Department of Education
http://www.ed.gov/about/offices/list/ies/index.html
Wisconsin Center for Educational Research, University of Wisconsin
http://www.wcer.wisc.edu/
Department of Psychology, University of Wisconsin
http://psych.wisc.edu/
Department of Psychology, Northeastern Illinois University
http://orion.neiu.edu/~deptpsyc/
Transition from Arithmetic to Algebraic Reasoning (TAAR)
http://labweb.education.wisc.edu/knuth/taar/