Torsten Grust Joachim Kröger Dieter Gluche Andreas Heuer Marc H. Scholl Query Evaluation in CROQUE - Calculus and Algebra Coincide. 84-100 1997 conf/bncod/1997 BNCOD db/conf/bncod/bncod97.html#GrustKGHS97 http://dx.doi.org/10.1007/3-540-63263-8_6