Complex sentence: He is alleged to have knowingly distributed books not approved by China's press and publication authority--it was alleged that some 4000 such books had been sent by post under false cover to 380 buyers in 28 cities in mainland China since October 2014.
Split into simpler sentences: He is alleged to have knowingly distributed books not approved by China's press and publication authority. It was alleged that some 4000 such books had been sent by post under false cover to 380 buyers in 28 cities since October 2014.