Perhaps you should try some spelling variations:
dung cong » dung trong
hieu cac » hieu luc, hieu va, hieu van
trang va » hang va
tran van » luan van
cong dan » cong san, cong tan, huong dan
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap
te sach » toc sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((te sach) or (hieu cac)) - hanh ((trang va) or (tran van)) dung cong dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((te sach) OR (hieu cac)) - hanh ((trang va) OR (tran van)) dung cong dan toan cau.
• Adding a wildcard symbol may retrieve word variants: hoc ((te sach) or (hieu cac)) - hanh ((trang va) or (tran van)) dung cong dan toan cau*.