Perhaps you should try some spelling variations:
hieu cua » hieu qua, dieu cua, bieu cua
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, nang ma
cac luc » cau luc, coc luc, cac cuoc
ca viet » va viet, co viet, san viet
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
dan va » doan va, dan ca, ban va

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