Perhaps you should try some spelling variations:
hoang cong » hang cong, hoang long, hoang vuong
hieu xanh » chieu xanh, hieu manh, hieu nganh
trang van » trang va, trong van, tang van
doc hieu » toc thieu, hoc thieu, hoc hien
tran van » luan van
cong dan » cong san, cong tan, huong dan
dan than » dan chan, ban than, van than
than cao » toan cao, thai cao, than cap

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc hieu xanh - hanh ((trang van) OR (tran van)) hoang cong dan than cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu xanh - hanh ((trang van) OR (tran van)) hoang cong dan than cao".
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - hanh ((trang van) OR (tran van)) hoang cong dan than cao*.