Perhaps you should try some spelling variations:
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, kho tang
hieu ve » hieu van
cam tuc » cam xuc, cam tu, nam thuc
so sac » so sach, so dac
dan vi » doan vi, don vi, dan va
va dan » ca dan, va dao, va dau
tuc va » thuc va, truc va, tuc xa
vi hoc » li hoc, va hoc
sac ky » cac ky, sai ky
ma hoi » mai hoi, ma hoa, me hoi
hien » bien, vien, tien

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sac ky tang ((ma hoi) OR (xa hoi)). ((hieu ve) or (hieu va)) cam tuc va dan vi hoc hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sac ky tang ((ma hoi) OR (xa hoi)). ((hieu ve) OR (hieu va)) cam tuc va dan vi hoc hien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sac ky tang ((ma hoi) OR (xa hoi)). ((hieu ve) or (hieu va)) cam tuc va dan vi hoc hien".
• Adding a wildcard symbol may retrieve word variants: so sac ky tang ((ma hoi) OR (xa hoi)). ((hieu ve) or (hieu va)) cam tuc va dan vi hoc hien*.