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
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
cua tre » cua te, cuu tre, cua triet
lang xa » lang ha, dang xay, lang van
nang xa » nang x, nang ma, mang xa
vi cua » vai cua, di cua
cam o » cham o, cam lo, ca o
o van » vo van, so van, do van

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: te sach ky ((nang xa) OR (lang xa)) hoi. ((hieu ve) OR (hieu va)) cam o van hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang xa) or (lang xa)) hoi. ((hieu ve) OR (hieu va)) cam o van hanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang xa) or (lang xa)) hoi. ((hieu ve) OR (hieu va)) cam o van hanh vi cua tre*.