TY - CPAPER AU - Andrew Olney BT - Cognitive and Metacognitive Educational Systems: Papers from the AAAI Fall Symposium (FS-09-02) LA - eng PY - 2009 T2 - Cognitive and Metacognitive Educational Systems: Papers from the AAAI Fall Symposium (FS-09-02) TI - GnuTutor: An Open Source Intelligent Tutoring System Based on AutoTutor ER -