The deaths in 1978 of both Ronnie Peterson and Gunnar Nilsson contributed to dropping the Swedis GP from the world championship . Interest for Formula One in Sweden fell following the death of these two Swedish racers . The deaths in 1978 of both Ronnie Peterson and Gunnar Nilsson contributed to the demise of this round of the world championship , as interest for Formula One in Sweden fell following the death of the two Swedish racers .