Perhaps you should try some spelling variations:
hoc thiet » hoc thieu, hoc thuyet, toc thieu
trang van » tran van, trang va, trong van
dung cong » dung trong
tan thanh » tran thanh, tang thanh, toan thanh
thanh cau » thanh chau, thanh mau, nhanh cau
tram van » tran van, tam van, tranh van
cong tan » cong tac, cong san, cong thanh

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc thiet) OR (hoc hien)) tach - hanh ((tram van) OR (trang van)) dung cong tan thanh cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc thiet) OR (hoc hien)) tach - hanh ((tram van) or (trang van)) dung cong tan thanh cau~".
• Adding a wildcard symbol may retrieve word variants: ((hoc thiet) OR (hoc hien)) tach - hanh ((tram van) or (trang van)) dung cong tan thanh cau*.