@workingPaper{BoleyAndelElsberndHerfertSintekStein_1993,
title={RELFUN guide : programming with relations and functions made easy},
author={Boley, Harold and Andel, Simone and Elsbernd, Klaus and Herfert, Michael and Sintek, Michael and Stein, Werner},
doi={http://dx.doi.org/10.22028/D291-25337},
year={1993}
}