Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
cam tuc » cam xuc, cam tu, dam thuc
tai cua » thai cua, tai cuc, tri cua
va dung » van dung, va duong, vat dung
sach ky » sac ky, sach y, sach ty
hieu va » lieu va
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky dang xa hoi. ((hieu va) OR (hieu qua)) ((cam tuc) or (nam thuc)) va dung tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang xa hoi. ((hieu va) OR (hieu qua)) ((cam tuc) OR (nam thuc)) va dung tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang xa hoi. ((hieu va) OR (hieu qua)) ((cam tuc) or (nam thuc)) va dung tai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang xa hoi. ((hieu va) OR (hieu qua)) ((cam tuc) or (nam thuc)) va dung tai cua tre*.