Perhaps you should try some spelling variations:
hoc viet » hoc hien
nam thuc » nam thuoc, am thuc, nam thu
va viet » hoa viet, san viet, mai viet
hanh di » hanh vi, hanh de, hang di
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
lai hoi » dai hoi, lai hoa, lai roi
mai hoi » mai khoi, dai hoi, mai doi
ve nam » he nam, va nam, le nam

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((mai hoi) or (lai hoi)). hieu ve nam thuc va hanh di ((va viet) or (hoc viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((mai hoi) OR (lai hoi)). hieu ve nam thuc va hanh di ((va viet) OR (hoc viet)).
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((mai hoi) or (lai hoi)). hieu ve nam thuc va hanh di ((va viet) or (hoc viet))*.