Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
day thanh » dao thanh, dat thanh, da thanh
hieu van » hieu va, thien van, lieu va
thanh vi » hanh vi, thanh va, thanh ve
thuc day » thuc dan, thuc vat
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
cao hoi » cau hoi, co hoi, cao hoc
cua tre » cua te, cuu tre, cua triet
tu sach » thu sach, su sach, te sach

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