Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, va tinh, le thanh
tu sach » thu sach, su sach, tu cach
te sach » toc sach
xang xa » lang xa, mang xa, ang xa
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
cu tren » tu tren, dua tren
y xang » ty xang
va cu » va cau, va chu, va su

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (te sach)) y xang xa hoi. hieu van cau duc ((va thanh) OR (ban thanh)) va cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) y xang xa hoi. hieu van cau duc ((va thanh) OR (ban thanh)) va cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (te sach)) y xang xa hoi. hieu van cau duc ((va thanh) OR (ban thanh)) va cu tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (te sach)) y xang xa hoi. hieu van cau duc ((va thanh) OR (ban thanh)) va cu tren*.