Perhaps you should try some spelling variations:
thieu sach » chieu sach, thien hach, hieu cach
hoc thieu » toc thieu, hoc hien
trinh vat » trinh van, trinh luat, sinh vat
cong vang » cong lang, cong quang, cong ngang
cong san » cong tac
toan cao » toan ban, toan tap
tinh va » tich va, trinh van, tinh gia

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc thieu sach - hoang ((tinh va) OR (trinh vat)) nhung ((cong vang) or (cong san)) toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thieu sach - hoang ((tinh va) OR (trinh vat)) nhung ((cong vang) OR (cong san)) toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thieu sach - hoang ((tinh va) OR (trinh vat)) nhung ((cong vang) or (cong san)) toan cao".
• Adding a wildcard symbol may retrieve word variants: hoc thieu sach - hoang ((tinh va) OR (trinh vat)) nhung ((cong vang) or (cong san)) toan cao*.