as to- you are comparing something regarding- concerning something in reference- referring something regarding and reference are similar

Nelson, these words are for the most part interchangeable. One difference is that "as to" is almost always used at the beginning of of sentence, to indicate a new topic. Example: That's all I have to say about sales. As to expenses, I want to make the following remarks." Also, "about" gets used in ways that the other three don't. For example: He told me about his trip to England. You would never use the other three in place of about in these sentences. "About" can also mean very soon or close to; the other three don't have this meaning. Example: He is about to leave. She is about 1.6 meters tall.

could you offer some concrete examples or situations?

what is the difference between referring and concerning? in chinese they all translate into a same word, i can't distinguish clearly.

as to- you are comparing something regarding- concerning something in reference- referring something regarding and reference are similar