Perhaps you should try some spelling variations:
dang xay » dang van, van xay
van hanh » van thanh, ban hanh, van anh
hanh mai » hanh ma, hanh mau, hanh may
va triet » va thiet, va trien, ve triet
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
dang xa » lang xa, dang ha, dang va
hieu va » lieu va, hieu qua
cac tuc » cac toc, cac tu, cac tac
tuc van » thuc van, truc van, tuc 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 ((dang xa) or (dang xay)) hoi. hieu va cac tuc van hanh mai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xa) OR (dang xay)) hoi. hieu va cac tuc van hanh mai va triet.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xa) or (dang xay)) hoi. hieu va cac tuc van hanh mai va triet*.