Zhu Xi (朱熹, Wade-Giles Chu Hsi, 1130 - 1200) in China was a Confucian and one of most significant Neo-Confucians. He taught at the famous White Deer Grotto Academy for some time. Considered unorthodox in their time, the Song Dynasty (960-1279), he and his fellow scholars added additional classic books: the Four Books, the Great Learning, and the Doctrine of Mean. Their writings were not widely recognised in Zhu Xi's time; however they subsequently became accepted as standard commentaries on the Confucian classics.