Perhaps you should try some spelling variations:
vien dai » hien dai
vien sau » vien da, nien su, vien cac
va tinh » may tinh
cac loc » cac lop, cac toc, cac hoc
hieu va » lieu va, hieu qua
ky danh » ky anh, ky dang
ky tang » ky nang, ky dang, kho tang
loc va » hoc va, luc va
te san » te ban, ke san, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: te san ((ky tang) or (ky danh)) xa hoi. hieu va cac loc va tinh ((vien sau) OR (vien dai)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te san ((ky tang) OR (ky danh)) xa hoi. hieu va cac loc va tinh ((vien sau) OR (vien dai)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te san ((ky tang) or (ky danh)) xa hoi. hieu va cac loc va tinh ((vien sau) OR (vien dai)) tren".
• Adding a wildcard symbol may retrieve word variants: te san ((ky tang) or (ky danh)) xa hoi. hieu va cac loc va tinh ((vien sau) OR (vien dai)) tren*.