 Complete the following phrase:  The 1981 CART PPG Indy Car World Series season, the third in the CART era of U.S. open-wheel racing, consisted of 11 races, beginning in Avondale, Arizona on March 22 and concluding at the same location on October 31. The PPG Indy Car World Series Drivers Champion was Rick Mears despite missing Round 2 at Milwaukee due to injuries sustained in the 