Perhaps you should try some spelling variations:
cach thuc » anh thuc, cac thu
hieu van » hieu va, thien van, lieu va
cac thuc » cac thu, can thuc, cay thuc
sach ky » sac ky, sach y, sach ty
duc cua » doc cua, luc cua, tuc cua
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, x ho
minh » dinh

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach ky) or (cac ky)) nang x hoi. hieu van ((cac thuc) OR (cach thuc)) van minh duc cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (cac ky)) nang x hoi. hieu van ((cac thuc) OR (cach thuc)) van minh duc cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (cac ky)) nang x hoi. hieu van ((cac thuc) OR (cach thuc)) van minh duc cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (cac ky)) nang x hoi. hieu van ((cac thuc) OR (cach thuc)) van minh duc cua tre*.