1. School of Teacher Education, 1000 E. University Ave., University of Wyoming, Laramie, WY, USA
2. Departamento de Matemáticas, Universidad Pedagógica Nacional Francisco Morazán, Tegucigalpa, Honduras
3. Math & Science Academy for Teachers, Los Alamos National Laboratory, Los Alamos, NM, USA
4. Education Department, University of California, Santa Cruz, Santa Cruz, CA, USA