Perhaps you should try some spelling variations:
hanh dai » hanh tai, hanh dao, vanh dai
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
cua tre » cuu tre, cua triet, dua tren
duc van » duc va, duc tan, duc manh
dau duc » dao duc, dang duc, dau nuoc
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
va dau » va dao
cua te » cua tu

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 y ((nang xa) or (nang ma)) hoi. hieu va dau duc van hanh dai ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((nang xa) OR (nang ma)) hoi. hieu va dau duc van hanh dai ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((nang xa) or (nang ma)) hoi. hieu va dau duc van hanh dai ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: su sach y ((nang xa) or (nang ma)) hoi. hieu va dau duc van hanh dai ((cua tre) OR (cua te))*.