Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
ky lang » ky nang, ky dang, ky tang
va hanh » van hanh, va thanh, ban hanh
cao hoc » co hoc, cho hoc, chat hoc
hieu va » lieu va, hieu qua
xoa doi » hoa doi
su xac » pu xac, su cac
va cao » va cac, va co, va dao
tai va » thai va, mai va, tri va
xac ky » cac ky, sac ky, bac ky
ha hoi » hoa hoi, xa hoi, va hoi
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 xac ky lang ((((ha hoi) OR (ha noi))) or (xoa doi)). hieu va cao hoc va hanh tai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su xac ky lang ((((ha hoi) OR (ha noi))) OR (xoa doi)). hieu va cao hoc va hanh tai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su xac ky lang ((((ha hoi) OR (ha noi))) or (xoa doi)). hieu va cao hoc va hanh tai va thiet".
• Adding a wildcard symbol may retrieve word variants: su xac ky lang ((((ha hoi) OR (ha noi))) or (xoa doi)). hieu va cao hoc va hanh tai va thiet*.