Boonen, A., H. Reed, J. Schoonenboom, and J. Jolles. “It’s Not a Math Lesson - we’re Learning to Draw! Teachers’ Use of Visual Representations in Instructing Word Problem Solving in Sixth Grade of Elementary School”. Frontline Learning Research, vol. 4, no. 5, Dec. 2016, pp. 34-61, doi:10.14786/flr.v4i5.245.