Perhaps you should try some spelling variations:
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, nang ma
cac hoc » cach hoc, cac hop, bac hoc
via cua » gia cua, gian cua, giau cua
y nang » ky nang, ly nang, v nang
va dan » va dao, va dau, va dap
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 y nang xa hoi. hieu qua ((cac nuoc) or (cac hoc)) ((va dan) OR (ca dan)) via cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang xa hoi. hieu qua ((cac nuoc) OR (cac hoc)) ((va dan) OR (ca dan)) via cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang xa hoi. hieu qua ((cac nuoc) or (cac hoc)) ((va dan) OR (ca dan)) via cua viet".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang xa hoi. hieu qua ((cac nuoc) or (cac hoc)) ((va dan) OR (ca dan)) via cua viet*.