Perhaps you should try some spelling variations:
hieu thien » chieu chien, dieu khien, bieu hien
hieu hien » bieu hien, dieu hien, chieu chien
hach xuc » thach duc, cach xu, mach xu
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
hanh xu » hanh tu, hanh sua, hanh cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
chu tre » cho tre, chu tri, cuu tre
nang o » nang co, nang ho, nang ro
va chu » va che, va cau, va chi
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)) ((hach xuc) or (hanh xu)) va tinh va chu 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)) ((hach xuc) OR (hanh xu)) va tinh va chu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o hoc. ((hieu thien) OR (hieu hien)) ((hach xuc) or (hanh xu)) va tinh va chu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hoc. ((hieu thien) OR (hieu hien)) ((hach xuc) or (hanh xu)) va tinh va chu tre*.