Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
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 triet, dua tren, cua thep
cuu tre » cau tren, cau treo
y nang » ky nang, ly nang, v nang
cua te » cua tu
x hoi » xa hoi, o hoi, x ho

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