Jens Dittrich Lukas Blunschi Marcos Antonio Vaz Salles Dwarfs in the rearview mirror: how big are they really? 1586-1597 2008 1 PVLDB 2 http://www.vldb.org/pvldb/1/1454230.pdf db/journals/pvldb/pvldb1.html#DittrichBS08