Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hang dau » hang va, hang tai
tu sach » su sach, te sach, tu cach
dau cua » dai cua, day cua, cau cua
va hang » van hang, va nang, va lang
cac luc » cau luc, coc luc, cac nuoc
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va
luc va » duc va, tuc va, loc va
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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) OR (thu sach)) ky nang o hoi. ((hieu va) OR (hieu qua)) cac luc va hang dau cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang o hoi. ((hieu va) OR (hieu qua)) cac luc va hang dau cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang o hoi. ((hieu va) OR (hieu qua)) cac luc va hang dau cua tre*.