Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, nam thu, nam tu
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
sach xa » sach dao, sach nha, sach bai
xa nang » da nang, va nang, xa nong
cao hoi » cau hoi, co hoi, cao hoc
va hanh » va thanh, va danh, ban hanh
di va » dai va, di vao, doi 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: su sach xa nang cao hoi. hieu van ((am thuc) or (nam thuc)) ((va hanh) or (van hanh)) di va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach xa nang cao hoi. hieu van ((am thuc) OR (nam thuc)) ((va hanh) OR (van hanh)) di va thiet.
• Adding a wildcard symbol may retrieve word variants: su sach xa nang cao hoi. hieu van ((am thuc) or (nam thuc)) ((va hanh) or (van hanh)) di va thiet*.