He also invested in a shopping mall in Columbus, Ohio. He has talked about some of those who have helped him over the years in business: "I couldn't have learned about business without a parade of teachers guiding me... from Milton Friedman to Donald Trump... and now, Les Wexner and Warren Buffett. I even learned a thing or two from Planet Hollywood, such as when to get out! And I did!" He has significant ownership in Dimensional Fund Advisors, an investment firm. Schwarzenegger is also the owner of Arnold's Sports Festival, which he started in 1989 and is held annually in Columbus, Ohio. It is a festival that hosts thousands of international health and fitness professionals which has also expanded into a three-day expo. He also owns a movie production company called Oak Productions, Inc. and Fitness Publications, a joint publishing venture with Simon & Schuster.
What investment firm does Schwarzenegger maintain partial ownership of?
{'text': 'Dimensional Fund Advisors', 'answer_start': 422}