Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cua viet » ca viet, hoa viet, cua dieu
sach ty » sach y, sach tu, sach thu
cao hoi » cau hoi, co hoi, cao hoc
nam duc » nam duoc, pham duc, nam thuc
duc van » duc va, duc tan, duc manh

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach doi) or (sach ty)) nang cao hoi. hieu van nam duc van hanh vi ((cua viet) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach doi) OR (sach ty)) nang cao hoi. hieu van nam duc van hanh vi ((cua viet) OR (cua vat)).
• Adding a wildcard symbol may retrieve word variants: tu ((sach doi) or (sach ty)) nang cao hoi. hieu van nam duc van hanh vi ((cua viet) or (cua vat))*.