Complex sentence: He has been mentioned in several op-ed articles by Dr. A.Q. Khan, a key figure behind Pakistan's clandestine nuclear weapons project, who began working for the government of Pakistan in 1975.
Split into simpler sentences: He has been mentioned in several op-ed articles by Dr. A.Q. Khan. Dr. Khan was a key figure behind Pakistan's clandestine nuclear weapons project and began working for the government of Pakistan in 1975.