Perhaps you should try some spelling variations:
cach thuc » anh thuc, cac thu
cac thuc » cac thu, can thuc, cay thuc
tu sach » thu sach, su sach, te sach
doan vi » don vi, doan thi, doan van
cua tre » cua te, cuu tre, cua triet
sach tu » sach thu, cach tu, sach ty
hieu ve » hieu va, hieu van
hang xa » hoang xa, hang va, hang ca
tu hang » thu hang, tu hanh, tu hung

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 tu hang xa hoi. hieu ve ((cac thuc) OR (cach thuc)) dan ((doan va) or (doan vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tu hang xa hoi. hieu ve ((cac thuc) OR (cach thuc)) dan ((doan va) OR (doan vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach tu hang xa hoi. hieu ve ((cac thuc) OR (cach thuc)) dan ((doan va) or (doan vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach tu hang xa hoi. hieu ve ((cac thuc) OR (cach thuc)) dan ((doan va) or (doan vi)) cua tre*.