 Complete the following phrase:  Indianapolis Motor Speedway president John Cooper was instrumental in forming a joint body of CART and USAC with the creation of the Championship Racing League in March 1980. However, in mid 1980, Cooper forced USAC to renounce their agreement with the CRL if they wanted to keep officiating the Indy 500. After USACs attempt at a 500-mile races at Pocono Raceway  which was boycotted by the CART teams, forcing USAC to fill the field with silver crown cars  USAC and CART eventually settled into a relatively peaceful co-existence, with USAC continuing to sanction the Indianapolis 500, and CART including the race in its schedule. USAC continued to sanction the Indy 500 until 1997, when the Indy Racing League itself product of the second American open-wheel split in 1996 terminated the sanctioning agreement following 