Suppose that you are the president of Peking University of Traditional Medicine and invite Prof. Hopkinson, an American medical expert, to attend a conference held in Beijing on 1st December, 2006. You want to write a letter of invitation to Prof. Hopkinson.
You should write appropriately 100 words. Do not sign your own name at the end of your letter. Use "Li Ming" instead. You do not need to write the address.