Complex sentence: Boris Christoff (Bulgarian:) (May 18,1914, Plovdiv, Bulgaria--June 28,1993, Rome, Italy) was a Bulgarian opera singer, one of the greatest basses of the 20th century.
Split into simpler sentences: Boris Christoff (Bulgarian:) (May 18,1914, Plovdiv, Bulgaria--June 28,1993, Rome, Italy) was a Bulgarian opera singer. He is considered to have been one of the greatest basses of the 20th century.