Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
so sanh » do sanh
va nang » van nang, da nang, cam nang
nang xa » nang x, lang xa, nang ma
qua cac » cua cac
cac toc » cac toi, cac nuoc, cac thoi
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (so sanh)) va nang xa hoi. hieu qua cac toc ((va hanh) OR (van hanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sanh)) va nang xa hoi. hieu qua cac toc ((va hanh) OR (van hanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sanh)) va nang xa hoi. hieu qua cac toc ((va hanh) OR (van hanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sanh)) va nang xa hoi. hieu qua cac toc ((va hanh) OR (van hanh)) vi cua tre*.