Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
dang xay » dang van, van xay
cac thuc » cach thuc, cac thu, can thuc
tu sach » thu sach, su sach, te sach
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
lang xa » lang ha, lang van
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: tu sach ky ((dang xay) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cac thuc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xay) OR (lang xa)) hoi. ((hieu ve) OR (hieu van)) cac thuc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((dang xay) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cac thuc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xay) or (lang xa)) hoi. ((hieu ve) OR (hieu van)) cac thuc va hanh vi cua tre*.