http://doi.acm.org/10.1145/181550.181565 db/journals/sigmod/Loeffen94.html Arjan Loeffen Text Databases: A Survey of Text Models and Systems. 97-106 sigmodR/23-1/P097.pdf 1994 23 SIGMOD Record 1 db/journals/sigmod/sigmod23.html#Loeffen94 http://www.acm.org/sigmod/record/issues/9403/Text.ps