Perhaps you should try some spelling variations:
nang dai » nang dau, nang tai, lang dai
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
dai hoi » dai hoc, dai hai, dai moi
ve cham » va cham, ve chat, vu cham
vu kham » vu khanh
va hanh » va thanh, va danh, ban hanh
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 ky nang dai hoi. hieu ((ve cham) or (vu kham)) xuc ((va hanh) OR (van hanh)) vi va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang dai hoi. hieu ((ve cham) OR (vu kham)) xuc ((va hanh) OR (van hanh)) vi va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang dai hoi. hieu ((ve cham) or (vu kham)) xuc ((va hanh) OR (van hanh)) vi va thiet".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang dai hoi. hieu ((ve cham) or (vu kham)) xuc ((va hanh) OR (van hanh)) vi va thiet*.