Perhaps you should try some spelling variations:
tu trong » tu tuong, tu tieng
thanh ve » hanh ve, thanh va, thanh vien
duc ban » duc tan, duc van, dua ban
vuc ban » vu ban, cuc ban, vua ban
so sach » so sanh, bo sach, co sach
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua
vu nang » vuc nang, va nang, vu dang
va cao » va cac, va co, va dao
x hoi » o hoi, x ho, 5 hoi
ve tu » ve thu, va tu, ve su

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach vu nang ((x hoi) or (xa hoi)). hieu va cao ((vuc ban) OR (duc ban)) thanh ve tu trong~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach vu nang ((x hoi) OR (xa hoi)). hieu va cao ((vuc ban) OR (duc ban)) thanh ve tu trong.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach vu nang ((x hoi) or (xa hoi)). hieu va cao ((vuc ban) OR (duc ban)) thanh ve tu trong".
• Adding a wildcard symbol may retrieve word variants: so sach vu nang ((x hoi) or (xa hoi)). hieu va cao ((vuc ban) OR (duc ban)) thanh ve tu trong*.