Perhaps you should try some spelling variations:
hoc thieu » hoc hien
dung cong » dung trong
tung tan » cung tan, hung tan, tang tan
tung dan » dung dan, huong dan, trung dai
cong tac » cong ty
tac tren » rac tren, tai tren, tap tren
tren tau » tren thuc, tren may, tren dat

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc thieu) or (toc thieu)) xanh - thanh ((tung tan) OR (tung dan)) dung cong tac tren tau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc thieu) OR (toc thieu)) xanh - thanh ((tung tan) OR (tung dan)) dung cong tac tren tau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc thieu) or (toc thieu)) xanh - thanh ((tung tan) OR (tung dan)) dung cong tac tren tau".
• Adding a wildcard symbol may retrieve word variants: ((hoc thieu) or (toc thieu)) xanh - thanh ((tung tan) OR (tung dan)) dung cong tac tren tau*.