Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
nam thuc » nam thuoc, am thuc, nam tu
van hanh » van thanh, ban hanh, van anh
vu sach » vu bach, su sach, vu khach
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua

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 y nang x ho. ((hieu van) or (hieu va)) ((nam thuc) OR (nam thu)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach y nang x ho. ((hieu van) OR (hieu va)) ((nam thuc) OR (nam thu)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach y nang x ho. ((hieu van) or (hieu va)) ((nam thuc) OR (nam thu)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: vu sach y nang x ho. ((hieu van) or (hieu va)) ((nam thuc) OR (nam thu)) van hanh vi cua tre*.