Complex sentence: A pan-democracy gathering held in Central on 27 January 2010 was attended by approximately 4,000 people, according to organisers; police gave the number at 1,900.
Split into simpler sentences: A pan-democracy gathering was held in Central on 27 January 2010, during which approximately 4,000 people were present, according to organisers. The police gave the number at 1,900.