Perhaps you should try some spelling variations:
cau treo » cau theo, cau tren, cau triet
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
cua tre » cua te, cuu tre, cua triet
toc ba » toc pa
toc ta » toc tay, toc thai

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 xa hoi. hieu qua cac ((toc ba) OR (toc ta)) don vi ((cau treo) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu qua cac ((toc ba) OR (toc ta)) don vi ((cau treo) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. hieu qua cac ((toc ba) OR (toc ta)) don vi ((cau treo) or (cua tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu qua cac ((toc ba) OR (toc ta)) don vi ((cau treo) or (cua tre))*.