Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu 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
di cua » doi cua, de cua, do cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang ((ma hoa) or (mai hoi)). hieu van cac dat va hanh ((di cua) OR (dai cua)) vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((ma hoa) OR (mai hoi)). hieu van cac dat va hanh ((di cua) OR (dai cua)) vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((ma hoa) or (mai hoi)). hieu van cac dat va hanh ((di cua) OR (dai cua)) vat".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((ma hoa) or (mai hoi)). hieu van cac dat va hanh ((di cua) OR (dai cua)) vat*.