Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang co » nang cao, nang doc, nang noi
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
thuc va » thuc vat, thuc dan, thuc day
cac cau » cac mau, bac cau, cac cam
can cau » van cau, ban cau, can chu
va dan » ca dan, va dao, va dau
ca cau » cua cau, ca cac, co cau

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 co hoc. hieu ve cham thuc va dan ((((ca cau) or (cac cau))) or (can cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang co hoc. hieu ve cham thuc va dan ((((ca cau) OR (cac cau))) OR (can cau)) tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang co hoc. hieu ve cham thuc va dan ((((ca cau) or (cac cau))) or (can cau)) tren*.