Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
thanh vi » hanh vi, thanh va, thanh ve
tac dat » tac da, tac dao, tac dau
hac dat » hoc dat, hoach dat, nhac dan
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
ma hoi » mai 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: thu sach ty nang ((ma hoi) or (xa hoi)). hieu van ((hac dat) OR (tac dat)) ban thanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty nang ((ma hoi) OR (xa hoi)). hieu van ((hac dat) OR (tac dat)) ban thanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty nang ((ma hoi) or (xa hoi)). hieu van ((hac dat) OR (tac dat)) ban thanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: thu sach ty nang ((ma hoi) or (xa hoi)). hieu van ((hac dat) OR (tac dat)) ban thanh vi cua vat*.