Yang Xiu
Zhang Su looked very different from his brother as he was a tall man with an imposing and majestuous appearance while Zhang Song was a rather short man who did not exercise restraint and was known as debauched. However, Zhang Song was also a very knowledgeable man with a good discernment hence he possessed talent and ability. When Liu Zhang sent him to Cao Cao, Cao Cao wasn't polite to him. But the current master of records Yang Xiu deeply respected him. And even recommended Cao Cao to have Zhang Song joined his personal staff but Cao Cao didn't listen to him. When Yang Xiu showed him the military books that Cao Cao had written, Zhang Song quickly had all of them read and memorized them through and through. After this event, Yang Xiu esteemed him even more.