 Complete the following phrase:  Jörgen Mårtensson born December 4, 1959 is one of the most successful Swedish orienteer of all times. Twice a winner of the World Orienteering Championships, he also won the 5 days O-Ringen in 1981 at age 21, 1996 and 1997 at age 37. Furthermore, he won the Swedish Championship in Marathon at Stockholm Marathon in 1993 . Now retired, he had one of the longest spanning careers in orienteering at world class level, taking part in World Championships over a period of twenty years. Starting with the 1978 World Orienteering Championships, where he placed eighth in the individual contest, he competed in every world championship until 