Perhaps you should try some spelling variations:
sach thi » sach thu, sach thieu, sach tham
thanh do » thanh de, thanh pho, thanh hoa
sach tai » sach bai, sach tham, sach dao
thanh di » thanh doi, thanh de, thanh dinh
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
hang ca » hang va, nang cao, hang tai
cam tu » cam thu, nam tu, dam tu
ca hoi » cau hoi, cua hoi, xa hoi
va cam » va cham, va cac, va cao

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach thi) or (sach tai)) hang ca hoi. hieu va cam tu va ((thanh di) OR (thanh do)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach thi) OR (sach tai)) hang ca hoi. hieu va cam tu va ((thanh di) OR (thanh do)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach thi) or (sach tai)) hang ca hoi. hieu va cam tu va ((thanh di) OR (thanh do)) cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach thi) or (sach tai)) hang ca hoi. hieu va cam tu va ((thanh di) OR (thanh do)) cua tre*.