Perhaps you should try some spelling variations:
hieu sach » chieu sach, hieu cach, dien sach
cong vang » cong lang, cong quang, cong ngang
vang toan » van toan, dang toan, quang toan
doc hieu » toc thieu, hoc thieu, hoc hien
trung ha » trung hoc, trung tam, trung cap
toan cao » toan ban, toan tap
lang ha » long ha

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 sach - hanh ((lang ha) or (trung ha)) trong cong vang toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sach - hanh ((lang ha) OR (trung ha)) trong cong vang toan cao*.