Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
van cham » van chat, van tham, va cham
hieu van » hieu va, thien van, lieu va
hang dau » hang tai
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach lo » sach dao, sach doi, sach hoi
su tien » su kien, su hien, tu tieng

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 lo ((hang dau) or (hang va)) hoi. hieu van cham thuc va ((hanh va) OR (hanh vi)) su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach lo ((hang dau) OR (hang va)) hoi. hieu van cham thuc va ((hanh va) OR (hanh vi)) su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach lo ((hang dau) or (hang va)) hoi. hieu van cham thuc va ((hanh va) OR (hanh vi)) su tien".
• Adding a wildcard symbol may retrieve word variants: tu sach lo ((hang dau) or (hang va)) hoi. hieu van cham thuc va ((hanh va) OR (hanh vi)) su tien*.