Radu Sion Mikhail J. Atallah Sunil Prabhakar Resilient Information Hiding for Abstract Semi-structures. 141-153 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2939&spage=141 2003 conf/iwdw/2003 IWDW db/conf/iwdw/iwdw2003.html#SionAP03