title: on the semantics of `` now '' in databases. authors: j clifford , c dyreson , t isakowitz , c jensen , r snodgrass. venue: acm trans . database syst .. year: 1997.0
title: on the semantics ofâ ?? nowâ ?? in databases j clifford , c dyreson , t isakowitz , cs jensen , rt acm transactions on database systems , 1997.0. authors: nan. venue: nan. year: nan