Yin refers to the place where the sun can't shine. In this paper, the yin of China and South Korea should refer to the south bank of Hanshui River.

Heyang: the north bank of the Yellow River. "River" was the proper name of the Yellow River in ancient times. When "yin" and "yang" are used to indicate the position of mountains and rivers, the south of the mountain is yang and the north of the mountain is yin; The water in the north is yang, and the water in the south is yin.

Almost all the reference books used before translated "Hebei" into "North Bank of the Yellow River".

However, there is another explanation that it is reasonable to translate the place name "Heyang" into "north of Heyang" instead of "north bank of the Yellow River".