《新唐书·列传·卷四十六》
以后，每日与诸王及姜皎等人入侍太子，只有王琚常参与密谋。
日以诸王及姜皎等入侍，独琚常豫秘谋。
After that, Wang Ju attended on the crown prince together with other princes and Jiang Jiao every day. However, only Wang Ju often took part in secret plots.