《资治通鉴·唐纪·唐纪三十》
开元二十八年春季，正月癸巳，玄宗往骊山温泉。
开元二十八年庚寅，公元七四零年
In the spring of the 28th year of the Kaiyuan era (740), on the Gengshen day of the first lunar month, Emperor Xuanzong went to Li Mountain Hot Spring.