Perhaps you should try some spelling variations:
hien xanh » hien hanh, hien nhanh, chieu xanh
hanh hang » thanh hang, hang hang, hanh han
hai thong » hai thuong, hai phong, hai trong
hang hai » hoang hai, hang tai, thanh hai
tong tap » tuong tac, trong tan, cong tac
cong tan » cong tac, cong san, cong thanh
doan cau » doan dau, doan cap, doanh chau
toan cau » toan cao, toan ban, toan tap

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hien xanh - hanh hang hai thong ((tong tap) OR (cong tan)) ((doan cau) OR (toan cau))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hien xanh - hanh hang hai thong ((tong tap) or (cong tan)) ((doan cau) OR (toan cau))~".
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - hanh hang hai thong ((tong tap) or (cong tan)) ((doan cau) OR (toan cau))*.