Perhaps you should try some spelling variations:
duong cong » dung cong, luong cong, duong trong
tang vanu » dang van, tan van, lang van
cong manh » cong danh, duong manh, cong thanh
manh toan » thanh toan, anh tuan, tinh toan
hieu cac » hieu luc, hieu van, vien cac
tang van » dang van, hoang van, trong van
toan ban » van ban
hieu va » lieu va, hieu qua

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu cac) or (hieu va)) - hanh ((tang vanu) or (tang van)) duong cong manh toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu cac) OR (hieu va)) - hanh ((tang vanu) OR (tang van)) duong cong manh toan ban.
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu cac) or (hieu va)) - hanh ((tang vanu) or (tang van)) duong cong manh toan ban*.