Valentine, S., Vides, F., Lucchese, G., Turner, D., Kim, H.- hoe, Li, W., Linsey, J. and Hammond, T. (2012) “Mechanix: A Sketch-Based Tutoring and Grading System for Free-Body Diagrams”, AI Magazine, 34(1), p. 55. doi: 10.1609/aimag.v34i1.2437.