What are the famous ancient books for learning hard pen calligraphy?

Practice Yan Zhenqing's regular script first, and advise you to practice the inscription on the multi-pagoda induction of Qianfu Temple in Xijing, Datang, because this kind of calligraphy has reached a large scale, and it is a fine regular script of Yan style, which is similar to the current habit, with small font and easy to master. Then buy Evonne, a thousand-character book-thin gold book (expensive and thin, Huizong first), so that you can learn the elegance of regular script. Then I am learning running script or cursive script. Why don't I let you learn Liu Gongquan's regular script because it is extremely difficult to write and easy to write. Although thin gold calligraphy is regular script, many strokes are close to running script. . [Don't write official script, you practice in vain. You can't write a swallowtail silkworm head with a pen or an ordinary marker. It's a waste of effort. If you stay here and have nothing to do, you can practice the official script "Zhang Qianbei" with a brush. Don't three fly together!