Historical evidence from China proves that Hoang Sa and Changsha Islands belong to Viet Nam. How to defend such evidence?

Objectively speaking, it is very difficult. Because Chinese civilization has always been a loess civilization, China people have always been indifferent to the ocean, and this is still the case. Ask people around you about the land area of China. I believe most people know a rough figure, but no one knows it, but if you ask about the area of the territorial sea, I'm afraid few people know it. However, it is ridiculous to use ancient maps to demonstrate the territorial problems between countries today. Because An Lan in history and Viet Nam in today's society used to be a vassal state of the Chinese empire, the national boundaries, whether on land or at sea, are the result of conventions, mainly determined by national strength.