Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
hanh tai » thanh tai, hang tai, hinh tai
tay thai » lay thai, toc thai, y thai
so sach » so sanh, bo sach, co sach
han tai » hang tai, nhan tai, van tai
hieu ve » hieu va, hieu van
tay hoi » tay ho, tao hoi
sach ly » sach y, sach lo, sach ty
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 ((tay hoi) or (tay thai)). hieu ve cau thuc vat ((hanh tai) OR (han tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ly hang ((tay hoi) OR (tay thai)). hieu ve cau thuc vat ((hanh tai) OR (han tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ly hang ((tay hoi) or (tay thai)). hieu ve cau thuc vat ((hanh tai) OR (han tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ly hang ((tay hoi) or (tay thai)). hieu ve cau thuc vat ((hanh tai) OR (han tai)) cua tre*.