Peter T. Wood Alberto O. Mendelzon Paolo Atzeni Idempotent Single-Predicate Horn Clauses. 129-143 ICDT1988/P129.pdf 1988 ICDT db/conf/icdt/icdt88.html#WoodMA88 conf/icdt/88 http://dx.doi.org/10.1007/3-540-50171-1_8 journals/siamcomp/AhoSU79 conf/popl/AhoU79 conf/sigmod/BancilhonR86 journals/siamcomp/BeeriV84 conf/stoc/ChandraM77 persons/Codd72 conf/pods/CosmadakisK86 conf/sigmod/CruzMW87 conf/vldb/Ioannidis85 conf/pods/Naughton86 conf/pods/NaughtonS87 conf/pods/Sagiv85a journals/siamcomp/Sagiv88 journals/jacm/SagivY80 books/cs/Ullman82