Perhaps you should try some spelling variations:
hieu luan » hieu luat, hieu quan, tieu luan
luan pham » luan phan, tuan pham, quan pham
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
duc van » duc va, duc tan, duc manh
van anh » van thanh, tuan anh, van minh
x hoi » xa hoi, o hoi, 5 hoi
vi su » ve su, ki su, oi 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 ty nang ((x hoi) OR (x ho)). hieu luan pham duc van anh ((vi su) OR (va su)) viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((x hoi) OR (x ho)). hieu luan pham duc van anh ((vi su) or (va su)) viet~".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((x hoi) OR (x ho)). hieu luan pham duc van anh ((vi su) or (va su)) viet*.