Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
van cac » van hac, van cau, van bac
y nang » ky nang, ly nang, v nang
toc xa » tuc xa, toc ta, hoc xa
vi cua » vai cua, di cua
cua tu » cua tuc, cua su, cua cu
x hoi » xa hoi, o hoi, 5 hoi

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: su sach y nang ((x hoi) OR (x ho)). hieu van cac ((toc xa) OR (hoc ma)) hanh vi cua tu~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang ((x hoi) OR (x ho)). hieu van cac ((toc xa) or (hoc ma)) hanh vi cua tu~".
• Adding a wildcard symbol may retrieve word variants: su sach y nang ((x hoi) OR (x ho)). hieu van cac ((toc xa) or (hoc ma)) hanh vi cua tu*.