Complex sentence: Donal Neil "Mike" O'Callaghan (September 10,1929 March 5,2004) was the 23rd Governor of the U.S. state of Nevada from 1971 until 1979.
Split into simpler sentences: Donal Neil "Mike" O'Callaghan (September 10,1929 March 5,2004) was an American politician. He was the 23rd Governor of the U.S. state of Nevada from 1971 until 1979.