thank you Mr ivan for the reply em really sorry that i forgot to mention that em not going to jiangxi university for studying rather i was asked to come to the university for one month for delivering lecture in medicine,as i've three years of teaching experience in a medical college in pakistan,so do i need original visa notice sheet for that too or invitation letter is sufficient for that,if i require the visa notice sheet how much time the university might need to get that from foreign office china