Perhaps you should try some spelling variations:
quan nhung » qua nhung, cua nhung, luan chung
cong thanh » dong thanh, cong trinh, cong tan
hien xanh » hien hanh, hien nhanh, chieu xanh
cong manh » cong danh, duong manh, hoang manh
canh ban » can ban, canh dan, canh van
toan cao » toan ban, toan tap
can van » cac van, can ban, tan van

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hien xanh - ((canh ban) or (can van)) quan nhung ((cong manh) OR (cong thanh)) toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hien xanh - ((canh ban) OR (can van)) quan nhung ((cong manh) OR (cong thanh)) toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hien xanh - ((canh ban) or (can van)) quan nhung ((cong manh) OR (cong thanh)) toan cao".
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - ((canh ban) or (can van)) quan nhung ((cong manh) OR (cong thanh)) toan cao*.