Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
duc ban » duc tan, duc van, duc man
dua ban » dia ban, cua ban, qua ban
hanh ki » hanh vi, hanh ky, hanh kien
su viet » so viet
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai
ki su » ky 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 v nang o hoi. hieu va cac ((duc ban) OR (dua ban)) hanh ki su viet~.
• Adding a wildcard symbol may retrieve word variants: tu sach v nang o hoi. hieu va cac ((duc ban) or (dua ban)) hanh ki su viet*.