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
hanh di » hanh de, hang di, danh di

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