Dimitri Theodoratos Aris Tsois Heuristic Optimization of OLAP Queries in Multidimensionally Hierarchically Clustered Databases. 2001 DOLAP http://www.cis.drexel.edu/faculty/song/DOLAP2001/Theodoratos%20-%207.pdf db/conf/dolap/dolap2001.html#TheodoratosT01