Perhaps you should try some spelling variations:
thanh vien » nhan vien, thanh van
ban thanh » ban hanh, ban hang
su sach » so sach, vu sach
vien ca » vien cac, vien cao, vien can
duc ban » duc tan, duc van, dua ban
sach tu » sach thu, cach tu, sach ty
ca viet » va viet, co viet, hoa viet
tu xang » ty xang, tu lang, tu quang
va cam » va cham, va cac, va cao
ve cac » va cac, vien cac
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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 tu xang ((o hoi) OR (o hai)). hieu ((ve cac) or (va cam)) duc ban thanh vien ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu xang ((o hoi) OR (o hai)). hieu ((ve cac) OR (va cam)) duc ban thanh vien ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tu xang ((o hoi) OR (o hai)). hieu ((ve cac) or (va cam)) duc ban thanh vien ca viet".
• Adding a wildcard symbol may retrieve word variants: su sach tu xang ((o hoi) OR (o hai)). hieu ((ve cac) or (va cam)) duc ban thanh vien ca viet*.