Perhaps you should try some spelling variations:
sach van » sach han, sach va, cach van
bach van » bach dan, cach van, bach dang
qua ban » cua ban, qua quan
duc ban » duc tan, duc van, dua ban
su viet » so viet
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
x hoi » xa hoi, o hoi, x ho
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 van) OR (bach van)) nang x hoi. hieu ve cac ((duc ban) OR (qua ban)) hanh vi su viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach van) OR (bach van)) nang x hoi. hieu ve cac ((duc ban) or (qua ban)) hanh vi su viet~".
• Adding a wildcard symbol may retrieve word variants: tu ((sach van) OR (bach van)) nang x hoi. hieu ve cac ((duc ban) or (qua ban)) hanh vi su viet*.