Perhaps you should try some spelling variations:
cham thuc » pham thuc, tham thuc, pham thuoc
nham thuc » nhan thuc, nam thuc, nham thu
day hanh » day nhanh, day thanh, dao hanh
sach ky » sac ky, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di 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 (sach y)) nang cao hoi. hieu ve ((cham thuc) OR (nham thuc)) day hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach y)) nang cao hoi. hieu ve ((cham thuc) OR (nham thuc)) day hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach y)) nang cao hoi. hieu ve ((cham thuc) OR (nham thuc)) day hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang cao hoi. hieu ve ((cham thuc) OR (nham thuc)) day hanh vi cua tre*.