Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
tai duc » tai cuc, mai duc, tai du
va daoh » va danh, va doanh
cac duc » cac du, cao duc, cac dac
sach ky » sac ky, sach y, sach ty
duc tre » duoc tren, duc tien
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, kho tang
ma hoi » mai hoi, ma hoa, me hoi
va dao » ca dao
ve cac » va cac, vien cac

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang ((ma hoi) OR (xa hoi)). hieu ve cac duc ((va daoh) OR (va dao)) tai duc tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang ((ma hoi) OR (xa hoi)). hieu ve cac duc ((va daoh) or (va dao)) tai duc tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang ((ma hoi) OR (xa hoi)). hieu ve cac duc ((va daoh) or (va dao)) tai duc tre*.