Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
cua tre » cuu tre, cua triet, dua tren
xuc va » duc va, tuc va, xac va
luc va » duc va, tuc va, loc va
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach vu nang xa hoi. hieu qua cac ((xuc va) or (luc va)) hanh vi ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach vu nang xa hoi. hieu qua cac ((xuc va) OR (luc va)) hanh vi ((cua tre) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: doc sach vu nang xa hoi. hieu qua cac ((xuc va) or (luc va)) hanh vi ((cua tre) or (cua te))*.