Perhaps you should try some spelling variations:
chiet tach » chieu sach
trong toan » truong toan, trong tan, trong hoan
hieu lang » chieu sang, hieu quang, nhieu tang
hanh hang » thanh hang, hang hang, hanh han
thang bac » thanh bac, thong bac, bang bac
hang qua » hang quan, hang cua, hanh qua
qua dung » quang dung, su dung, qua song
hang ban » hang luan, hang va, hang tai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ho ((hieu lang) or (chiet tach)) - hanh hang qua dung trong toan ((thang bac) OR (hang ban))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((hieu lang) OR (chiet tach)) - hanh hang qua dung trong toan ((thang bac) OR (hang ban)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) or (chiet tach)) - hanh hang qua dung trong toan ((thang bac) OR (hang ban))".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) or (chiet tach)) - hanh hang qua dung trong toan ((thang bac) OR (hang ban))*.