Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
vien cac » vien bach, vien dai, vien da
tu sach » thu sach, su sach, te sach
duc ban » duc tan, duc van, duc man
dua ban » dia ban, cua ban, qua 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 vien cac ((duc ban) or (dua 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 vien cac ((duc ban) OR (dua ban)) hanh vi su viet*.