Jose Torres-Jimenez Carlos de Alfonso Vicente Hernández Computation of Ternary Covering Arrays Using a Grid. 240-246 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3285&spage=240 2004 conf/aacc/2004 AACC db/conf/aacc/aacc2004.html#Torres-JimenezAH04