Alfred V. Aho Jeffrey D. Ullman The Universality of Data Retrieval Languages. 110-120 1979 POPL db/conf/popl/popl79.html#AhoU79 db/conf/popl/AhoU79.html POPL/00001702.PDF POPLs1/POPL1979/P110.PDF books/aw/AhoHU74 journals/siamcomp/AhoSU79 ... journals/cacm/Codd70 persons/Codd72 ... conf/stoc/ChandraM77 books/aw/Date75 ... journals/ipl/Paredaens78 journals/siamcomp/Schnorr78 journals/cacm/SmithC75 conf/vldb/SagivY78 ... journals/ibmsj/Zloof77