Allen Van Gelder Rodney W. Topor Safety and Translation of Relational Calculus Queries. 235-278 1991 16 ACM Trans. Database Syst. 2 db/journals/tods/tods16.html#GelderT91 http://doi.acm.org/10.1145/114325.103712 db/journals/tods/GelderT91.html TODS16/P235.PDF ... ... conf/pods/BeeriNRST87 persons/Codd72 conf/eds/Decker86 journals/jacm/Demolombe92 journals/cacm/DershowitzM79 journals/jacm/Paola69a journals/jacm/Fagin82 conf/popl/HallHT75 conf/jcdkb/Kifer88 ... conf/pods/Kuper87 journals/jlp/LloydT84 books/cs/Maier83 conf/icalp/Makowsky81 ... conf/iclp/MorrisUG86 books/cs/NaqviT89 journals/acta/Nicolas82 ... ... journals/tcs/Topor87 conf/vldb/TsurZ86 books/cs/Ullman88 books/cs/Ullman82 conf/pods/GelderT87 journals/ipl/Vardi81