Perhaps you should try some spelling variations:
hieu vien » hieu hien, thieu nien, hieu tieng
hieu viec » nhieu viec, hieu ve, sieu viet
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
va dan » ca dan, va dau, va dap
va dao » ca dao
cac bo » bac bo, cac co

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 nang xa hoi. ((hieu vien) OR (hieu viec)) cac bo ((va dan) or (va dao)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. ((hieu vien) OR (hieu viec)) cac bo ((va dan) OR (va dao)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. ((hieu vien) OR (hieu viec)) cac bo ((va dan) or (va dao)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. ((hieu vien) OR (hieu viec)) cac bo ((va dan) or (va dao)) vai cua tre*.