Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
hieu va » lieu va, hieu qua
ky lang » ky nang, ky dang, ky tang
hoa hoi » khoa hoi, hoa hoc, hoc hoi
va hanh » van hanh, va thanh, ban hanh
hoa doi » hoa dai, xoa doi, hoa duoc
cao hoc » co hoc, cho hoc, chat hoc
hoc doi » hoc dai, hoc noi, hoc moi
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
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 ((hoa hoi) or (((hoa doi) OR (hoc 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 ((hoa hoi) OR (((hoa doi) OR (hoc 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 ((hoa hoi) or (((hoa doi) OR (hoc doi)))). hieu va cao hoc va hanh tai va thiet".
• Adding a wildcard symbol may retrieve word variants: su xac ky lang ((hoa hoi) or (((hoa doi) OR (hoc doi)))). hieu va cao hoc va hanh tai va thiet*.