Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
vanh dai » van dai, vanh tai, van dao
thuc dan » thuc hanh, hoc dan, thuc vat
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
dang xa » dang xay, lang xa, dang ha
sac ky » cac ky, sai ky
va nam » van nam, ha nam, va nay

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 y) or (sac ky)) dang xa hoi. hieu va nam thuc dan ((vanh dai) OR (lanh dao)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach y) OR (sac ky)) dang xa hoi. hieu va nam thuc dan ((vanh dai) OR (lanh dao)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach y) or (sac ky)) dang xa hoi. hieu va nam thuc dan ((vanh dai) OR (lanh dao)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach y) or (sac ky)) dang xa hoi. hieu va nam thuc dan ((vanh dai) OR (lanh dao)) cua tre*.