Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
ty tang » tay tang, ty hang, ky tang
hieu vu » hieu va, hieu ve, hieu su
vu pham » su pham, vi pham, vu kham
va hanh » va thanh, va danh, ban hanh
lam cua » nam cua, lam chat
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ((ty tang) or (ty xang)) ma hoi. hieu vu pham duc ((va hanh) OR (van hanh)) lam cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((ty tang) OR (ty xang)) ma hoi. hieu vu pham duc ((va hanh) OR (van hanh)) lam cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((ty tang) or (ty xang)) ma hoi. hieu vu pham duc ((va hanh) OR (van hanh)) lam cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ((ty tang) or (ty xang)) ma hoi. hieu vu pham duc ((va hanh) OR (van hanh)) lam cua tre*.