@conferenceObjectPart{SuAikenNiehrenPriesnitzTreinen_2002,
title={First-order theory of subtyping constraints},
author={Su, Zhendong and Aiken, Alexander and Niehren, Joachim and Priesnitz, Tim and Treinen, Ralf},
doi={http://dx.doi.org/10.22028/D291-25769},
year={2002}
}