Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
sai ky » sac ky
ve cac » va cac, vien cac
ma hoi » xa hoi, ma hoa, me hoi
di cua » doi cua, de cua, do cua
su sai » su tai, su hai, su dai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sai ky nang ((ma hoi) or (mai hoi)). hieu ve cac duc van hanh ((di cua) OR (dai cua)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sai ky nang ((ma hoi) OR (mai hoi)). hieu ve cac duc van hanh ((di cua) OR (dai cua)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sai ky nang ((ma hoi) or (mai hoi)). hieu ve cac duc van hanh ((di cua) OR (dai cua)) triet".
• Adding a wildcard symbol may retrieve word variants: su sai ky nang ((ma hoi) or (mai hoi)). hieu ve cac duc van hanh ((di cua) OR (dai cua)) triet*.