@article{DBLP:journals/aiedu/LynchAPA09,
author = {Collin Lynch and
Kevin D. Ashley and
Niels Pinkwart and
Vincent Aleven},
title = {Concepts, Structures, and Goals: Redefining Ill-Definedness},
journal = {I. J. Artificial Intelligence in Education},
volume = {19},
number = {3},
year = {2009},
pages = {253-266},
ee = {http://iospress.metapress.com/content/t337qmr215841n15/},
bibsource = {DBLP, http://dblp.uni-trier.de}
}