Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
va triet » va trien, ve triet, cua triet
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
hanh va » hang va, hanh vi
co sach » bo sach, cuon sach, hoc sach
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
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: co sach y ((nang ma) or (sang ma)) hoi. hieu van nam thuc van hanh va ((va triet) or (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach y ((nang ma) OR (sang ma)) hoi. hieu van nam thuc van hanh va ((va triet) OR (va thiet)).
• Adding a wildcard symbol may retrieve word variants: co sach y ((nang ma) or (sang ma)) hoi. hieu van nam thuc van hanh va ((va triet) or (va thiet))*.