Multiple Interactive Representations for Fractions Learning. - Laurens Feenstra; Vincent Aleven; Nikol Rummel; Niels Taatgen (Intelligent Tutoring Systems (2), 2010)

Thinking with Your Hands: Interactive Graphical Representations in a Tutor for Fractions Learning. - Laurens Feenstra; Vincent Aleven; Nikol Rummel; Martina A. Rau; Niels Taatgen (AIED, 2011)