《资治通鉴·齐纪·齐纪四》
直将军周奉叔和曹道刚二人，平时就是萧昭业的心腹，于是，命令二人同时主管殿中值班宿卫。过了几天，又任命曹道刚为黄门郎。
直阁周奉叔、曹道刚素为帝心膂，并使监殿中直卫；少日，复以道刚为黄门郎。
Lieutenant General Zhou Fengshu and Cao Daogang were both confidants of Xiao Zhaoye, so he ordered the two of them to jointly oversee the guards on duty in the palace. Several days later, he once again appointed Cao Daogang as Yellow Gate Attendant.