My lawyer says if some of them

are not available, the doucments of the highest degree should be included. My understanding is that these documants are just basic materials showing the immigration officers your background. If you are really difficult to get the documents, just include the highest one. In fact, it is not hard to ask the friends in china to help you get the documents for both chinese and english versions. Now most universities in china would like to issue these documents, which is a prevalent bussiness to make money. It is not difficult.