Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cau tren » cu tren, ca tren, cau treo
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cac luc » cau luc, coc luc, cac nuoc
va dan » ca dan, va dao, va dap
va dau » va dao

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x ho. hieu va cac luc ((va dan) OR (va dau)) vi ((cau tren) OR (dau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x ho. hieu va cac luc ((va dan) OR (va dau)) vi ((cau tren) or (dau tren))~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. hieu va cac luc ((va dan) OR (va dau)) vi ((cau tren) or (dau tren))*.