Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hanh tai » thanh tai, hang tai, han tai
thai hoa » thai khoa, thai hoc, thi hoa
tai hoa » tai khoa, thi hoa, dai hoa
bo sach » co sach
hieu ve » hieu va, hieu van
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
y hang » ly hang, ty hang, yu hang
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: ((hoc sach) or (bo sach)) y hang ((tai hoa) or (thai hoa)). hieu ve cau truc va hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (bo sach)) y hang ((tai hoa) OR (thai hoa)). hieu ve cau truc va hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (bo sach)) y hang ((tai hoa) or (thai hoa)). hieu ve cau truc va hanh tai cua tre*.