Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
tu cach » tu cac
danh vi » hanh vi, dinh vi, danh di
va danh » va dinh, va dan, va hanh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
te sach » toc sach
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 cach) or (te sach)) ky tang ma hoa. ((hieu ve) OR (hieu va)) cau thuc va danh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (te sach)) ky tang ma hoa. ((hieu ve) OR (hieu va)) cau thuc va danh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (te sach)) ky tang ma hoa. ((hieu ve) OR (hieu va)) cau thuc va danh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (te sach)) ky tang ma hoa. ((hieu ve) OR (hieu va)) cau thuc va danh vi cua tre*.