Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
van cau » van dau, van hau, van chat
duc ban » duc tan, duc van, dua ban
su viet » so viet
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 van nang x hoi. hieu van cau ((duc ban) or (cua ban)) hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach van nang x hoi. hieu van cau ((duc ban) OR (cua ban)) hanh vi su viet*.