Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
va hanh » van hanh, va danh, ban hanh
sach ty » sach tu, sach thu, xach tay
cac dac » cac dan, cac dai, cac bac
hieu va » lieu va, hieu qua
xang xa » lang xa, mang xa, ang xa
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: so ((sach ty) OR (sach y)) xang xa hoi. hieu va cac dac ((va hanh) or (va thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach y)) xang xa hoi. hieu va cac dac ((va hanh) OR (va thanh)) vi cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) OR (sach y)) xang xa hoi. hieu va cac dac ((va hanh) or (va thanh)) vi cua tre*".