Renato Carmo Tomás Feder Yoshiharu Kohayakawa Eduardo Sany Laber Rajeev Motwani Liadan O'Callaghan Rina Panigrahy Dilys Thomas Querying priced information in databases: The conjunctive case. 2007 3 ACM Transactions on Algorithms 1 http://doi.acm.org/10.1145/1219944.1219955 db/journals/talg/talg3.html#CarmoFKLMOPT07