Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
ky tang » ky nang, ky dang, kho tang
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
cam tuc » cam xuc, cam tu, dam thuc
so sac » so sach, so dac
va dau » va dao
va dan » ca dan, va dao, va dap
vi hoc » li hoc, va hoc
sac ky » cac ky, sai ky
ma hoi » mai hoi, xa hoi, ma hoa
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. hieu ve ((cam tuc) or (nam thuc)) ((va dan) OR (va dau)) vi hoc hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sac ky tang ma hoi. hieu ve ((cam tuc) OR (nam thuc)) ((va dan) OR (va dau)) vi hoc hien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sac ky tang ma hoi. hieu ve ((cam tuc) or (nam thuc)) ((va dan) OR (va dau)) vi hoc hien".
• Adding a wildcard symbol may retrieve word variants: so sac ky tang ma hoi. hieu ve ((cam tuc) or (nam thuc)) ((va dan) OR (va dau)) vi hoc hien*.