conf/pods/87 Oded Shmueli Decidability and Expressiveness of Logic Queries. 237-249 1987 PODS db/conf/pods/pods87.html#Shmueli87 http://doi.acm.org/10.1145/28659.28685 journals/anthology/cd1-3:PODS87/P237.PDF journals/anthology/dvd1:text/1-3/PODS87/P237.PDF journals/siamcomp/AhoSU79 journals/jlp/ChandraH85 ... conf/sigmod/JarkeCV84 ... books/sp/Lloyd84 ... ... ... ... conf/pods/Sagiv87 ... journals/tods/Ullman85 conf/vldb/Warren81