@article{TUC-CSCW/LAPA409,
author = "C. Lynch and K. D. Ashley and N. Pinkwart and V. Aleven",
title = "Concepts, Structures, and Goals: Redefining Ill-Definedness",
year = 2009,
journal = "International Journal of Artificial Intelligence in Education",
volume = 19,
number = 3
}