Perhaps you should try some spelling variations:
khanh vai » khanh van, hanh vi, hanh va
dat khanh » van khanh, duy khanh
sach bai » sach dao, cac bai, sach xa
sach thi » sach thu, sach tai, sach thieu
cac toi » cac thoi
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
hanh ca » hanh cac, hanh cat, hanh cua
ca hoi » cau hoi, cua hoi, xa hoi
vai va » mai va, dai va, hai va
thiet » thieu

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((sach thi) or (sach bai)) hanh ca hoi. hieu va ((cac tuc) or (cac toi)) dat khanh vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((sach thi) OR (sach bai)) hanh ca hoi. hieu va ((cac tuc) OR (cac toi)) dat khanh vai va thiet.
• Adding a wildcard symbol may retrieve word variants: hoc ((sach thi) or (sach bai)) hanh ca hoi. hieu va ((cac tuc) or (cac toi)) dat khanh vai va thiet*.