Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
sach vu » sach va, sach tu, sach uu
vu lang » va lang, vu dang, cu lang
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
hanh va » hang va
su hien » su kien, su tien, thu hien
va cao » va cac, va co, va dao
su van » tu van, vu van

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach vu lang xa hoi. hieu va cao su van ((hanh va) or (hanh vi)) su hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach vu lang xa hoi. hieu va cao su van ((hanh va) OR (hanh vi)) su hien.
• Adding a wildcard symbol may retrieve word variants: thu sach vu lang xa hoi. hieu va cao su van ((hanh va) or (hanh vi)) su hien*.