Perhaps you should try some spelling variations:
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
dieu cua » dieu tra
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va dan » va dao, va dau, va dai
va dap » va dao, va dau
ca dan » cac dan, ca dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang xa hoi. hieu va cac nuoc ((((va dan) OR (va dap))) or (ca dan)) dieu cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu va cac nuoc ((((va dan) OR (va dap))) OR (ca dan)) dieu cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang xa hoi. hieu va cac nuoc ((((va dan) OR (va dap))) or (ca dan)) dieu cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu va cac nuoc ((((va dan) OR (va dap))) or (ca dan)) dieu cua tre*.