Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, tu cach
qua ban » cua ban, qua quan
hieu ve » hieu va, hieu van
su viet » so viet
te sach » toc sach
v nang » va nang, vu nang, van nang
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.

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) OR (te sach)) v nang x hoi. hieu ve cac ((dia ban) or (qua ban)) hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) v nang x hoi. hieu ve cac ((dia ban) OR (qua ban)) hanh vi su viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) v nang x hoi. hieu ve cac ((dia ban) or (qua ban)) hanh vi su viet*".