Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
hoc sach » hoc sinh, hoc cac, hoc anh
hieu va » lieu va, hieu qua
va hang » van hang, va lang, va hanh
va nang » van nang, da nang, cam nang
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach y nang x ho. ((hieu va) or (hieu van)) cam xuc ((va hang) OR (va nang)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach y nang x ho. ((hieu va) OR (hieu van)) cam xuc ((va hang) OR (va nang)) va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach y nang x ho. ((hieu va) or (hieu van)) cam xuc ((va hang) OR (va nang)) va cua tre".
• Adding a wildcard symbol may retrieve word variants: hoc sach y nang x ho. ((hieu va) or (hieu van)) cam xuc ((va hang) OR (va nang)) va cua tre*.