Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
van hanh » ban hanh, van anh, van ban
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
dang xa » dang xay, dang ha, dang va
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
cac tu » cac thu, cach tu, cac du
vai va » mai va, dai va, hai va
thiet » thieu

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 (lang xa)) hoi. hieu va cac tu ((van hanh) or (van thanh)) vai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((dang xa) OR (lang xa)) hoi. hieu va cac tu ((van hanh) OR (van thanh)) vai va thiet.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((dang xa) or (lang xa)) hoi. hieu va cac tu ((van hanh) or (van thanh)) vai va thiet*.