The solutions that Huanggang's exercise books can't find are: consulting relevant materials by yourself and looking for relevant books in the library or bookstore.

1. Check the relevant materials by yourself: You can use search engines or online learning resources to check the relevant materials by yourself and try to solve the problem.

2. Go to the library or bookstore to find relevant books: You can go to the library or bookstore to find relevant textbooks, reference books or problem sets and try to find the answer.