Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
nam danh » nam dan
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua

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: toc sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac nuoc ((nam danh) OR (nam dinh)) va cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac nuoc ((nam danh) or (nam dinh)) va cua tre~".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang xa hoi. ((hieu va) OR (hieu qua)) cac nuoc ((nam danh) or (nam dinh)) va cua tre*.