It wasn't really a disagreement. All of these chlorinated hydrocarbons can be used as dry cleaning agents. Whether it's perchloroethylene or trichlorethelyne just depends on whether we have one hydrogen instead of a chlorine. They're both feasible. Perchloroethylene is more economic, and that's the one more commonly used. Trichlorethelyne, or TCE, is the one that's been in the news a lot because it's more toxic.
On June 21st, 2006. See this statement in context.