Perhaps you should try some spelling variations:
lam thuc » lam thuoc, am thuc, nam thuc
trinh va » trinh van, trinh vat, trinh ve
trinh vi » trinh ve, trinh viet, trinh van
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
thuc va » thuc vat, thuc dan, thuc day
van lam » van nam
sach ky » sac ky, sach y, sach ty
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet

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