Perhaps you should try some spelling variations:
dieu hien » dieu khien, dieu kien, bieu hien
dieu hieu » dieu khien, dien chieu, dieu kien
cau treo » cau theo, cau tren, cau triet
cua tre » cua te, cuu tre, cua triet
va dinh » van dinh, va kinh, va tinh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
va cao » va cac, va co, va dao
cao va » cao van, tao va, co 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. ((dieu hieu) OR (dieu hien)) va cao va dinh van ((cua tre) or (cau treo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x hoi. ((dieu hieu) OR (dieu hien)) va cao va dinh van ((cua tre) OR (cau treo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x hoi. ((dieu hieu) OR (dieu hien)) va cao va dinh van ((cua tre) or (cau treo))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x hoi. ((dieu hieu) OR (dieu hien)) va cao va dinh van ((cua tre) or (cau treo))*.