In recent years, there are no designated reference materials for Tsinghua's postgraduate entrance examination, but the content of the examination will not exceed these two books: \x0d\ Circuit Principles by Jiang Jiguang \x0d\ Circuit Principles by Yu Xinjie \x0d\ and supporting problem sets, all written by Tsinghua, so the style of postgraduate entrance examination should be matched with these supporting problem sets in addition to the above two reference materials in previous years.