Complex sentence: Anders Olof Gunnar Källén (February 13,1926 in Kristianstad, Sweden--October 13,1968 in Hanover, West Germany in a plane accident) was a leading Swedish theoretical physicist and a professor at Lund University until his death at the age of 42.
Split into simpler sentences: Anders Olof Gunnar Källén (February 13,1926 in Kristianstad, Sweden--October 13,1968 in Hanover, West Germany in a plane accident). Källén was a leading Swedish theoretical physicist and a professor at Lund University until his death at the age of 42.