Higher mathematics emphasizes probability theory, although the score is not big, but the topic is more difficult. Probability theory is the most important thing for you who take the math test. If you start preparing for the postgraduate entrance examination now, you will have plenty of time. You can take the time to finish reading the book, get familiar with formulas and theorems, and then do some simple topics to consolidate it. Next, you can buy a reference book. I suggest you buy Shao Jian's books. His book is comprehensive in knowledge and full of questions, which is worth reading. Remember to do the sprint questions. Practice makes perfect.