Complex sentence: The following year, in the 1939 tour, the first mountain time trial was introduced to the tour, over the Col d'Iseran from Bonneval-sur-Arc to Bourg-Saint-Maurice, which was won by Sylvere Maes by a margin of four minutes.
Split into simpler sentences: The following year, in 1939, the first mountain time trial was introduced to the Tour. It went over the Col d'Iseran from Bonneval-sur-Arc to Bourg-Saint-Maurice and was won by Sylvere Maes by a margin of four minutes.