Perhaps you should try some spelling variations:
ban thanh » ban hang
ban hanh » ban hang
tham duc » pham duc, tham du, than duc
vu sach » vu bach, su sach, vu khach
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
sach tu » sach thu, cach tu, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach tu ((nang xa) OR (nang ma)) hoi. hieu va tham duc ((ban thanh) or (ban hanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach tu ((nang xa) OR (nang ma)) hoi. hieu va tham duc ((ban thanh) OR (ban hanh)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach tu ((nang xa) OR (nang ma)) hoi. hieu va tham duc ((ban thanh) or (ban hanh)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: vu sach tu ((nang xa) OR (nang ma)) hoi. hieu va tham duc ((ban thanh) or (ban hanh)) dai cua tre*.