necessary document for applying business visa for filipino who want to go to china

what are the necessarry document needed for applying a business visa for china.i am a filipino and work in korea for seven years.my company recently built factory in qingdao.they send me an INVITATION LETTER OF DULY AUTHORIZED UNIT from the state administration of foreign expert affairs of peoples republic of china.i am here in the philippines since my contract in korea ha been finish.any answers i really appreciated