Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
van hanh » van thanh, ban hanh, van anh
phan duc » pham duc, phan tu, phan dau
te sach » toc sach
hieu va » lieu va, hieu qua
hanh va » hang va, hanh vi
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
nang xa » nang x, lang xa, nang ma
va cua » va chua, via cua, ca cua

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) or (doc sach)) ky nang xa hoi. ((hieu ve) OR (hieu va)) phan duc van hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (doc sach)) ky nang xa hoi. ((hieu ve) OR (hieu va)) phan duc van hanh va cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (doc sach)) ky nang xa hoi. ((hieu ve) OR (hieu va)) phan duc van hanh va cua tre*".