Perhaps you should try some spelling variations:
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
ve giao » te giao, viet giao, van giao
va hanh » van hanh, va thanh, va danh
cau tre » cau tren, cau treo, cau tra
sac ky » cac ky, sai ky
da cau » dat cau, va cau

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: toc ((sach ky) OR (sac ky)) nang cao hoi. hieu ve giao duc ((va hanh) or (gia thanh)) da cau tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach ky) OR (sac ky)) nang cao hoi. hieu ve giao duc ((va hanh) OR (gia thanh)) da cau tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc ((sach ky) OR (sac ky)) nang cao hoi. hieu ve giao duc ((va hanh) or (gia thanh)) da cau tre".
• Adding a wildcard symbol may retrieve word variants: toc ((sach ky) OR (sac ky)) nang cao hoi. hieu ve giao duc ((va hanh) or (gia thanh)) da cau tre*.