Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
va hanh » van hanh, va thanh, va danh
cac dai » cac dan, cac bai, can dai
cac dat » cac dan, cai dat, cac dac
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
ma hoi » xa hoi, ma hoa, me hoi
vi cua » vai cua, di 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 ((ma hoi) or (mai hoi)). hieu van ((cac dat) OR (cac dai)) va hanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((ma hoi) OR (mai hoi)). hieu van ((cac dat) OR (cac dai)) va hanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((ma hoi) or (mai hoi)). hieu van ((cac dat) OR (cac dai)) va hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((ma hoi) or (mai hoi)). hieu van ((cac dat) OR (cac dai)) va hanh vi cua vat*.