Perhaps you should try some spelling variations:
hieu thien » chieu chien, dieu khien, bieu hien
hieu hien » bieu hien, dieu hien, chieu chien
thach duc » thach thuc, than duc, thinh duc
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
hanh tu » anh tu, danh tu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cho tre » cho thue, khoe tre
nang o » nang co, nang ho, nang ro
va cho » van cho, va co, va che
o hoc » co hoc, mo hoc, so hoc

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 o hoc. ((hieu thien) or (hieu hien)) ((thach duc) or (hanh tu)) va tinh va cho tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hoc. ((hieu thien) OR (hieu hien)) ((thach duc) OR (hanh tu)) va tinh va cho tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hoc. ((hieu thien) or (hieu hien)) ((thach duc) or (hanh tu)) va tinh va cho tre*.