Perhaps you should try some spelling variations:
trong van » trong cac
tang van » dang van, hoang van, tang luan
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
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 y ((tang van) OR (trong van)) hoi. hieu van nam thuc van hanh vi ((cua tre) or (hoa viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((tang van) OR (trong van)) hoi. hieu van nam thuc van hanh vi ((cua tre) OR (hoa viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((tang van) OR (trong van)) hoi. hieu van nam thuc van hanh vi ((cua tre) or (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((tang van) OR (trong van)) hoi. hieu van nam thuc van hanh vi ((cua tre) or (hoa viet))*.