Perhaps you should try some spelling variations:
hien xanh » hien hanh, hien nhanh, chieu xanh
cua thong » cua thuong, cua khong, cua tong
hua khong » hoa khong, cua khong, hoac khong
thong bai » thong tai, nhung bai, thong xay
anh tang » anh bang, anh dang, anh nang
bai toan » bai tap
toan cau » toan cao, toan ban, toan tap

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 - anh tang ((cua thong) or (hua khong)) thong bai toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hien xanh - anh tang ((cua thong) OR (hua khong)) thong bai toan cau.
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - anh tang ((cua thong) or (hua khong)) thong bai toan cau*.