conf/sigmod/81 Witold Litwin 19-29 1981 SIGMOD Conference db/conf/sigmod/sigmod81.html#Litwin81 SIGMOD81/P019.PDF http://doi.acm.org/10.1145/582318.582322 db/conf/sigmod/Litwin81.html books/aw/AhoHU74 journals/acta/BayerM72 journals/tods/BayerU77 journals/csur/Comer79 conf/sigmod/DeutscherST75 journals/tods/FaginNPS79 journals/is/GhoshL75 ... ... conf/sigmod/Knott71 books/aw/Knuth73 journals/bit/Larson78 conf/vldb/Larson80 ... ... conf/vldb/Litwin78 ... conf/vldb/Litwin80 conf/ifip/MalyK80 journals/cacm/Sprugnoli77