 Complete the following phrase:  Nevertheless, many Formula One drivers continued to drive the smaller and lighter cars on non-championship weekends, and some Grand Prix grids notably in Germany, where the long circuit at the Nürburgring could cope with large entries would be a mix of Formula One and Formula Two cars. Jacky Ickx made his Grand Prix debut at the Nürburgring in a Formula Two car in 1966. The following year Ickx qualified with the third fastest time overall but was forced to start behind even the slower Formula One cars. Ickx quickly forced his way back into a points position, only to be forced to retire with broken suspension. Jim Clark, regarded as one of the greatest race drivers of all time, was killed in a Formula Two race early in 1968, at the Hockenheimring. A year later Gerhard Mitter was killed at the Nürburgring while practising for the 