Marc Wichterich Ira Assent Philipp Kranen Thomas Seidl Efficient EMD-based similarity search in multimedia databases via flexible dimensionality reduction. 199-212 2008 SIGMOD Conference http://doi.acm.org/10.1145/1376616.1376639 conf/sigmod/2008 db/conf/sigmod/sigmod2008.html#WichterichAKS08