Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
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: toc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: toc sach y nang xa hoi. hieu qua cac luc van hanh di ((cua tre) or (cau tren))*.