Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
van cac » van hac, van cau, van bac
cac dat » cac dan, cai dat, cac dai
va hanh » van hanh, va thanh, va danh
va dan » ca dan, va dao, va dau
de cua » le cua, te cua, dieu cua

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 ky nang ((mai hoi) or (ma hoa)). hieu van cac dat ((va hanh) or (va dan)) de cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((mai hoi) OR (ma hoa)). hieu van cac dat ((va hanh) OR (va dan)) de cua vat.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((mai hoi) or (ma hoa)). hieu van cac dat ((va hanh) or (va dan)) de cua vat*.