Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
sach ky » sach y, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
luc van » luoc van, luu van, duc van
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
va nam » van nam, va nay
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: te ((sach ky) or (sac ky)) nang cao hoi. hieu ((va nam) OR (ha nam)) luc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sac ky)) nang cao hoi. hieu ((va nam) OR (ha nam)) luc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sac ky)) nang cao hoi. hieu ((va nam) OR (ha nam)) luc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (sac ky)) nang cao hoi. hieu ((va nam) OR (ha nam)) luc van hanh vi cua tre*.