Olivier Bodini Bertrand Nouvel Z-Tilings of Polyominoes and Standard Basis. 137-150 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3322&spage=137 2004 conf/iwcia/2004 IWCIA db/conf/iwcia/iwcia2004.html#BodiniN04