Please answer the following question: Given the below context:  The first group of people claiming to be an ambassadorial mission of Romans to China was recorded as having arrived in 166 AD by the Book of the Later Han. The embassy came to Emperor Huan of Han China from "Andun" (Chinese: 安敦; Emperor Antoninus Pius or Marcus Aurelius Antoninus), "king of Daqin" (Rome). As Antoninus Pius died in 161 AD, leaving the empire to his adoptive son Marcus Aurelius Antoninus, and the envoy arrived in 166 AD, confusion remains about who sent the mission, as both emperors were named "Antoninus". The Roman mission came from the south (therefore probably by sea), entering China by the frontier of Rinan or Tonkin (present-day Vietnam). It brought presents of rhinoceros horns, ivory, and tortoise shell, probably acquired in Southern Asia. The text states that it was the first time there had been direct contact between the two countries. Yule speculated that the Roman visitors must have lost their original wares due to robbery or shipwreck and used the gifts instead, prompting Chinese sources to suspect them of withholding their more precious valuables, which Yule notes was the same criticism directed at papal missionary John of Montecorvino when he arrived in China in the late 13th century AD. Historians Rafe de Crespigny, Peter Fibiger Bang, and Warwick Ball believe that this was most likely a group of Roman merchants rather than official diplomats sent by Marcus Aurelius. Crespigny stresses that the presence of this Roman embassy as well as others from Tianzhu (in northern India) and Buyeo (in Manchuria) provided much-needed prestige for Emperor Huan, as he was facing serious political troubles and fallout for the forced suicide of politician Liang Ji, who had dominated the Han government well after the death of his sister Empress Liang Na. Yule emphasised that the Roman embassy was said to come by way of Jiaozhi in northern Vietnam, the same route that Chinese sources claimed the embassies from Tianzhu (northern India) had used in 159 and 161 AD.  Guess a valid title for it!
A:
Sino-Roman relations