Querying priced information in databases: the conjunctive case - Carmo, Renato; Feder, Tomás; Kohayakawa, Yoshiharu; Laber, Eduardo Sany; Motwani, Rajeev; O'Callaghan, Liadan; Panigrahy, Rina; Thomas, Dilys (ACM Transactions on Algorithms (TALG), 2007)