xii List of Articles Worms, Concordat of Wu Zhao (Wu Chao) Wycliffe, John X Xixia (Hsi Hsia) Xuanzang (Hsuan-tsang) Xuanzong (Hsuan-tsung) Y Yarmuk, Battle of Yaroslav the Wise Yelu Chucai Yongle (Yung-lo) Yuan dynasty (1279–1368) Yue Fei (Yueh Fei) Z Zen (or Ch’an) Buddhism Zhao Kuangyin (Chao K’uang-yin) Zheng He (Cheng Ho) Zhu Xi (Chu Hsi) Zimbabwe