The four books are The Analects of Confucius, Mencius, University and The Doctrine of the Mean. Originally, The Analects of Confucius and Mencius had a low status, but they were not classics, but works explaining them. However, the status of The Analects of Confucius improved after the Wei and Jin Dynasties, and Mencius' status also improved after the publication of Justice by pseudo-Sun Shi in the Song Dynasty. The Great Learning and The Doctrine of the Mean were originally two books in the Book of Rites, which were later annotated by Zhu and called Disciples' Rules. Therefore, later generations regarded them as classics and have always been proposition textbooks for imperial examinations.