Wolf-Tilo Balke Skyline Queries for Preference-Based Information Systems. 3 2008 Grundlagen von Datenbanken http://www.i-u.de/fileadmin/be_user/PDF_Docs/IT_School/Technical_Reports/TR_01_2008.pdf conf/gvd/2008 db/conf/gvd/gvd2008.html#Balke08