I'm researching the kanji 本 for a blog post. I understand its original meaning is "root", and the other two senses, "book" and "this," are semantic shifts. I've found a couple of sources (without citations; one on Japanese StackExchange) for its sense of "book."
I'm having more trouble finding its sense of "this" as in 本学, 本件, 本状, 本品 and so on. Does anyone know how it came to be used in this way?