Perhaps you should try some spelling variations:
ban hanh » ban hang
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
va thanh » gia thanh, ban thanh, va tinh
va dinh » van dinh, va kinh, va tinh
su sach » so sach, vu sach
cac luc » cau luc, coc luc, cac nuoc
hieu ve » hieu va, hieu van
cao hoi » cau hoi, co hoi, cao hoc
so viet » hoc viet
ve cac » va cac, vien cac
hai so » dai so, tai so, thai son

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 thu nang cao hoi. hieu ve cac luc ((((ban hanh) or (va thanh))) or (va dinh)) hai so viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thu nang cao hoi. hieu ve cac luc ((((ban hanh) OR (va thanh))) OR (va dinh)) hai so viet.
• Adding a wildcard symbol may retrieve word variants: su sach thu nang cao hoi. hieu ve cac luc ((((ban hanh) or (va thanh))) or (va dinh)) hai so viet*.