Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach tai » sach bai, sach tham, sach dao
tai hanh » tai thanh, tai nhanh, thi hanh
hanh cau » nhanh cau, hang cau, hanh cac
hanh dai » hanh tai, hanh dao, vanh dai
cua viet » ca viet, cua vat, cua dieu
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
cac toi » cac thoi
va hanh » van hanh, va thanh, ban hanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach tai hanh cau hoi. hieu va ((cac tuc) or (cac toi)) va hanh dai ((cua viet) or (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach tai hanh cau hoi. hieu va ((cac tuc) OR (cac toi)) va hanh dai ((cua viet) OR (hoa viet)).
• Adding a wildcard symbol may retrieve word variants: toc sach tai hanh cau hoi. hieu va ((cac tuc) or (cac toi)) va hanh dai ((cua viet) or (hoa viet))*.