Perhaps you should try some spelling variations:
hieu tieng » viet tieng, dien tieng, tiep 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 bac, cac dac, cac tai
cac toc » cac toi, cac nuoc, cac thoi
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua
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 tieng) or (hieu hien)) ((cac tac) OR (cac toc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((hieu tieng) OR (hieu hien)) ((cac tac) OR (cac toc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((hieu tieng) or (hieu hien)) ((cac tac) OR (cac toc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((hieu tieng) or (hieu hien)) ((cac tac) OR (cac toc)) va hanh vi cua tre*.