Perhaps you should try some spelling variations:
hieu vien » hieu viec, thieu nien, hieu tieng
hieu hien » bieu hien, dieu hien, chieu chien
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cac tac » cac toc, cac bac, cac dac
va hanh » van hanh, va thanh, va danh
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
tac va » tac da, tac xa, tuc va
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: tu sach ky nang x hoi. ((hieu vien) or (hieu hien)) cac tac va hanh vi ((cuu tre) OR (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu vien) OR (hieu hien)) cac tac va hanh vi ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu vien) or (hieu hien)) cac tac va hanh vi ((cuu tre) OR (cua tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((hieu vien) or (hieu hien)) cac tac va hanh vi ((cuu tre) OR (cua tre))*.