Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
hieu va » lieu va, hieu qua
kem cua » em cua, keo cua, diem cua
luc van » luoc van, luu van, duc van
cam luc » cam xuc, cau luc
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky nang ((x hoi) OR (o hoi)). ((hieu ve) or (hieu va)) cam luc van hanh kem cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky nang ((x hoi) OR (o hoi)). ((hieu ve) OR (hieu va)) cam luc van hanh kem cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang ((x hoi) OR (o hoi)). ((hieu ve) or (hieu va)) cam luc van hanh kem cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ky nang ((x hoi) OR (o hoi)). ((hieu ve) or (hieu va)) cam luc van hanh kem cua tre*.