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
nang xa » nang x, lang xa, nang ma
va dinh » van dinh, va kinh, va tinh
dinh di » dinh du, dinh vi, danh di
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

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