Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
dua tren » dung tren
cau tren » cu tren, dau tren, ca tren
qua cac » cua cac
cac luc » cau luc, coc luc, cac nuoc
luc van » luoc van, luu van, duc van
nang xa » nang x, lang xa, nang ma
cuu tre » cua tre, cau treo
hanh di » hanh vi, hanh de, hang di
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van 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 v nang xa hoi. hieu qua cac luc van hanh di ((dua tren) or (((cuu tre) or (cau tren))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v nang xa hoi. hieu qua cac luc van hanh di ((dua tren) OR (((cuu tre) OR (cau tren)))).
• Adding a wildcard symbol may retrieve word variants: toc sach v nang xa hoi. hieu qua cac luc van hanh di ((dua tren) or (((cuu tre) or (cau tren))))*.