Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
dang xay » dang van, van xay
cau treo » cau theo, cau tren, cau triet
hoc sach » hoc sinh, hoc cac, hoc anh
xay hoi » xa hoi, tay hoi, cay phoi
cac luc » cau luc, coc luc, cac nuoc
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
v dang » vu dang, va dang, 2 dang
luc va » duc va, tuc va, loc va

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) OR (hoc sach)) v dang xay hoi. hieu va cac luc va hanh di ((cua tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) v dang xay hoi. hieu va cac luc va hanh di ((cua tre) OR (cau treo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) v dang xay hoi. hieu va cac luc va hanh di ((cua tre) or (cau treo))".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) v dang xay hoi. hieu va cac luc va hanh di ((cua tre) or (cau treo))*.