Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu va » lieu va, hieu qua
doan vi » doan va, don vi, doan thi
cac xuc » cam xuc, cac nuoc, chat xuc
hieu ve » hieu van
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
xuc va » duc va, tuc va, luc va
dan vi » don vi, dan va, gan vi

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

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