Christian S. Collberg Tapas Ranjan Sahoo Software watermarking in the frequency domain: Implementation, analysis, and attacks. 721-755 2005 13 Journal of Computer Security 5 http://iospress.metapress.com/openurl.asp?genre=article&issn=0926-227X&volume=13&issue=5&spage=721 db/journals/jcs/jcs13.html#CollbergS05