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
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
xuc va » duc va, tuc va, xac va
luc va » duc va, tuc va, loc va
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) OR (luc va)) hanh 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) OR (luc va)) hanh 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) OR (luc va)) hanh 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) OR (luc va)) hanh va cua tre*.