Perhaps you should try some spelling variations:
hieu luc » hieu luat, hieu qua
vu sach » vu bach, su sach, vu khach
sach ty » sach y, sach tu, sach thu
hanh di » hanh vi, hanh de, hang di
va hanh » van hanh, va thanh, va danh
hieu he » hiem he, hieu le, hieu hien
hieu ve » hieu va, hieu van
cao hoi » cau hoi, co hoi, cao hoc
ty nang » ky nang, ty xang, ty hang
ma thu » va thu
thu va » thuc va, thue va, tu va
di cua » dai cua, doi cua, de cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ty nang cao hoi. ((((hieu luc) or (hieu ve))) or (hieu he)) ma thu va hanh di cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ty nang cao hoi. ((((hieu luc) OR (hieu ve))) OR (hieu he)) ma thu va hanh di cua vat.
• Adding a wildcard symbol may retrieve word variants: vu sach ty nang cao hoi. ((((hieu luc) or (hieu ve))) or (hieu he)) ma thu va hanh di cua vat*.