Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, ca tren, cau treo
dau tren » dau tien, dat tren, dau tieng
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
cac luc » cau luc, coc luc, cac nuoc
luc van » luoc van, luu van, duc van
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang

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 y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) or (((cau tren) OR (dau tren))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) OR (((cau tren) OR (dau tren)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) or (((cau tren) OR (dau tren))))".
• Adding a wildcard symbol may retrieve word variants: doc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) or (((cau tren) OR (dau tren))))*.