Perhaps you should try some spelling variations:
tac danh » sach danh, cac doanh, cac dan
xac danh » xac dinh, sach danh, cac doanh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu he » hieu ve, hiem he, hieu le
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
sai cua » dai cua, hai cua, lai cua
he nam » ha nam, nghe nam

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 ((sang ma) OR (nang ma)) hoi. hieu he nam thu ((xac danh) or (tac danh)) sai cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((sang ma) OR (nang ma)) hoi. hieu he nam thu ((xac danh) OR (tac danh)) sai cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((sang ma) OR (nang ma)) hoi. hieu he nam thu ((xac danh) or (tac danh)) sai cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((sang ma) OR (nang ma)) hoi. hieu he nam thu ((xac danh) or (tac danh)) sai cua vat*.