Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
nang chat » nang cham, nang cao, nang suat
nang phat » nang suat, van phat
can cau » van cau, ban cau, cac cau
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
ve tham » va tham, ve cham, vi tham
va dan » ca dan, va dao, va dau
ca cau » cua cau, cac cau, ca cac

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