@Article{J19,
  key =		 {J19},
  author =	 {Marvin Schiller and Dominik Dietrich and Christoph Benzm{\"u}ller},
  title =	 {Proof Step Analysis for Proof Tutoring -- A Learning Approach to
Granularity},
  journal =	 {Teaching Mathematics and Computer Science},
  year =	 2008,
  number = 2,
  volume = 6,
  pages = {325-343},
}