Perhaps you should try some spelling variations:
hanh dong » anh dong, ha dong
nam thuc » nam thuoc, am thuc, nam thu
dong cua » dung cua, cong cua, huong cua
day hanh » day nhanh, day thanh, dao hanh
thuc day » thuc dan, thuc vat
hieu van » thien van, lieu va, hieu ve
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
sach ky » sach y, sach ty, sach kem
nang xa » nang x, lang xa, nang ma
sac ky » cac ky, sai ky

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

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