DTD XHTML-1.0-Transitional issue

We were trying to use the DTD XHTML-1.0-Transitional and found that the 
DTD/xhtml1-transitional.dtd file doesn't exist (
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd cannot be found). 
Is this a known issue?

Thanks,
Tony Phillips 
IBM Software Engineer 
Information Protection Services 
Business Continuity and Resiliency Services