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