Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
dua ban » dia ban, cua ban, qua ban
duc ban » duc tan, duc van, duc man
hieu ve » hieu va, hieu van
su viet » so viet
sach 2 » sach y
2 nang » v nang
ve cac » va cac, vien cac
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi
vi su » va su, ve su, ki su

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach 2 nang ((x hoi) OR (o hoi)). hieu ve cac ((duc ban) OR (dua ban)) hanh vi su viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach 2 nang ((x hoi) OR (o hoi)). hieu ve cac ((duc ban) or (dua ban)) hanh vi su viet~".
• Adding a wildcard symbol may retrieve word variants: tu sach 2 nang ((x hoi) OR (o hoi)). hieu ve cac ((duc ban) or (dua ban)) hanh vi su viet*.