The United States Patent And Trademark Office operates a website which has a Search capability. Anyone can look up a Trademark or an application for a Trademark, and find the official status. I just did this for Van K. Tharp's trademark Position Sizing and found that the USPTO recently mailed him an Office Action. They refused his application. He has six months to reply or his application will be considered abandoned. The Office Action letter from USPTO to Tharp is attached. So when you read that "Position Sizing is Trademarked by Van Tharp", it isn't true.