Perhaps you should try some spelling variations:
vu sach » vu bach, vu khach
va hanh » van hanh, va thanh, va danh
cac tac » cac toc, cac bac, cac dac
cac tuc » cac toc, cac tu, cac nuoc
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
su sach » so sach
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: ((vu sach) or (su sach)) ky lang xa hoi. hieu ve ((cac tuc) OR (cac tac)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (su sach)) ky lang xa hoi. hieu ve ((cac tuc) OR (cac tac)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (su sach)) ky lang xa hoi. hieu ve ((cac tuc) OR (cac tac)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (su sach)) ky lang xa hoi. hieu ve ((cac tuc) OR (cac tac)) va hanh vi cua tre*.