Complex sentence: Shiing-Shen Chern (October 26,1911--December 3,2004) was a Chinese American mathematician, one of the leaders in differential geometry of the twentieth century.
Split into simpler sentences: Shiing-Shen Chern (October 26,1911--December 3,2004) was a Chinese-born American mathematician. He was regarded as one of the leaders in differential geometry of the twentieth century.