Perhaps you should try some spelling variations:
su triet » su viet, ve triet
tu sach » thu sach, su sach, te sach
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
hoa doi » hoa dai, hoc doi, hoa duoc
ky tang » ky nang, ky dang, kho tang
su tien » su kien, su hien, tu tieng
va nam » van nam, ha nam, va nay
thu va » thuc va, thue va, tu va

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 tang ((hoa doi) or (xoa doi)). hieu va nam thu va hanh va ((su triet) OR (su tien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky tang ((hoa doi) OR (xoa doi)). hieu va nam thu va hanh va ((su triet) OR (su tien)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang ((hoa doi) or (xoa doi)). hieu va nam thu va hanh va ((su triet) OR (su tien))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang ((hoa doi) or (xoa doi)). hieu va nam thu va hanh va ((su triet) OR (su tien))*.