Perhaps you should try some spelling variations:
ban hang » ngan hang
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cac luc » cau luc, coc luc, cac nuoc
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
xang ma » nang ma, sang ma, rang ma
ve cac » va cac, vien cac
vi va » vi van, vai va, vu va
thiet » thieu

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 ty ((xang ma) or (tang ma)) hoi. hieu ve cac luc ((va hanh) or (ban hang)) vi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((xang ma) OR (tang ma)) hoi. hieu ve cac luc ((va hanh) OR (ban hang)) vi va thiet.
• Adding a wildcard symbol may retrieve word variants: su sach ty ((xang ma) or (tang ma)) hoi. hieu ve cac luc ((va hanh) or (ban hang)) vi va thiet*.