Guadalupe Canahuate Tan Apaydin Ahmet Sacan Hakan Ferhatosmanoglu Secondary bitmap indexes with vertical and horizontal partitioning. 600-611 2009 EDBT http://doi.acm.org/10.1145/1516360.1516430 conf/edbt/2009 db/conf/edbt/edbt2009.html#CanahuateASF09