Alexis-Julien Bouquet Olivier Serre Igor Walukiewicz Pushdown Games with Unboundedness and Regular Conditions. 88-99 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2914&spage=88 2003 conf/fsttcs/2003 FSTTCS db/conf/fsttcs/fsttcs2003.html#BouquetSW03