Perhaps you should try some spelling variations:
sieu viet » su viet, dien viet, bien viet
thanh dam » thanh dat, thanh nam, thanh tam
thanh dao » thanh dat, thanh do, hanh dao
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
co thuc » do thuc, co thua, mo thuc
qua co » qua con, cua co, qua ca
ma hoi » mai hoi, ma hoa, me hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky dang ((ma hoi) or (xa hoi)). hieu qua co thuc va ((thanh dao) OR (thanh dam)) sieu viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((ma hoi) OR (xa hoi)). hieu qua co thuc va ((thanh dao) OR (thanh dam)) sieu viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((ma hoi) or (xa hoi)). hieu qua co thuc va ((thanh dao) OR (thanh dam)) sieu viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((ma hoi) or (xa hoi)). hieu qua co thuc va ((thanh dao) OR (thanh dam)) sieu viet*.