Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
ve triet » va trien, su triet
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
vi ve » va ve, gi ve, ve ve

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang ma) or (tang ma)) hoi. hieu ve ((nam thuc) or (cam xuc)) van hanh vi ve triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang ma) OR (tang ma)) hoi. hieu ve ((nam thuc) OR (cam xuc)) van hanh vi ve triet.
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang ma) or (tang ma)) hoi. hieu ve ((nam thuc) or (cam xuc)) van hanh vi ve triet*.