Map of Kampuchea Krom

There is a diplomatic conflict among Cambodian with Vietnamese over the land Kampuchear Krom. Cambodian said it had been historically administrated by Cambodian. Vietnamese responded that South Vietnam had been administrating by Vietnam long centuries. What is the problem? It is about MAP and PAST TENSE AND PAST CONTINUE .

This is South Vietnam Map

 

This is Kampuchea Krom Map