Rafiul Ahad K. V. Bapa Rao Dennis McLeod On Estimating the Cardinality of the Projection of a Database Relation. 28-40 TODS14/P028.PDF 1989 14 ACM Trans. Database Syst. 1 db/journals/tods/tods14.html#AhadRM89 http://doi.acm.org/10.1145/62032.62034 db/journals/tods/AhadRM89.html ... journals/cacm/Cardenas73 journals/cacm/Cheung82 journals/is/Christodoulakis83 journals/cacm/Codd70 ... journals/cacm/Luk83 conf/vldb/MerrettO79 journals/cacm/Siler76 journals/cacm/WhangWS83 journals/tods/Yao77