Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
tay thai » lay thai, toc thai, y thai
tai cua » thai cua, tai cuc, tri cua
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
sach ly » sach y, sach lo, sach ty
tao hoi » tao khoi, tao boi, tay hoi
ly hang » ly quang
cua tre » cua te, cuu tre, cua triet
ve cau » ke cau, va cau, ve cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ly hang ((tao hoi) or (tay thai)). hieu ve cau thuc van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ly hang ((tao hoi) OR (tay thai)). hieu ve cau thuc van hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach ly hang ((tao hoi) or (tay thai)). hieu ve cau thuc van hanh tai cua tre*.