Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
nang dai » nang dau, nang tai, lang dai
tu sach » thu sach, su sach, te sach
dai hoi » dai hoc, dai hai, dai moi
ve cham » va cham, ve chat, vu cham
sach ky » sac ky, sach y, sach ty
vu kham » vu khanh
duc ban » duc tan, duc van, dua ban
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: tu sach ky nang dai hoi. hieu ((ve cham) or (vu kham)) duc ban thanh ((vi va) or (tu va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang dai hoi. hieu ((ve cham) OR (vu kham)) duc ban thanh ((vi va) OR (tu va)) thiet.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang dai hoi. hieu ((ve cham) or (vu kham)) duc ban thanh ((vi va) or (tu va)) thiet*.