Perhaps you should try some spelling variations:
lang dai » lang hai, lang mai, lang chai
san viet » gian viet, anh viet
cam thuc » am thuc, nam thuc, cam thu
sach va » sach ha, sach dao, sach nha
va viet » hoa viet, mai viet, dao viet
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va, hieu van
dai hoi » dai hoc, dai hai, dai moi
sach xa » sach dao, sach nha, sach bai
ve cam » ve cham, ve cac, va cam

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: co ((sach va) OR (sach xa)) lang dai hoi. hieu ve cam thuc va hanh va ((va viet) or (san viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co ((sach va) OR (sach xa)) lang dai hoi. hieu ve cam thuc va hanh va ((va viet) OR (san viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "co ((sach va) OR (sach xa)) lang dai hoi. hieu ve cam thuc va hanh va ((va viet) or (san viet))".
• Adding a wildcard symbol may retrieve word variants: co ((sach va) OR (sach xa)) lang dai hoi. hieu ve cam thuc va hanh va ((va viet) or (san viet))*.