Perhaps you should try some spelling variations:
hieu sach » chieu sach, hieu cach, hieu cac
dien sach » dien anh
cua chong » cua cong, cua chung, cuu chong
cua khong » hua khong, cua phuong, cua thuong
dan chinh » dang chinh, lan chinh, van chinh
chinh can » chinh ca, chinh ban, chinh cau
cong dan » cong san, cong tan, huong dan

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) or (dien sach)) - canh tranh ((cua chong) OR (cua khong)) cong dan chinh can~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sach) OR (dien sach)) - canh tranh ((cua chong) OR (cua khong)) cong dan chinh can.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sach) or (dien sach)) - canh tranh ((cua chong) OR (cua khong)) cong dan chinh can".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sach) or (dien sach)) - canh tranh ((cua chong) OR (cua khong)) cong dan chinh can*.