Perhaps you should try some spelling variations:
dieu hieu » dieu hien, dieu khien, dien chieu
cau treo » cau theo, cau tren, cau triet
hieu cac » hieu luc, hieu va, hieu van
cac cao » cac co, ca cao, bac cao
sach ky » sach y, sach ty, sach kem
va dinh » van dinh, va kinh, va tinh
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
nang o » nang co, nang ho, nang ro
cao va » cao van, tao va, co va
o hoi » co hoi, o hoc, o hai

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) OR (sac ky)) nang o hoi. dieu hieu cac 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) OR (sac ky)) nang o hoi. dieu hieu cac 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) OR (sac ky)) nang o hoi. dieu hieu cac cao va dinh van ((cua tre) or (cau treo))".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) nang o hoi. dieu hieu cac cao va dinh van ((cua tre) or (cau treo))*.