Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
hieu luat » hieu qua
kinh vai » kinh hai, kinh va, kinh van
hieu luc » hieu qua
nang xa » lang xa, nang ma, mang xa
sach ty » sach y, sach tu, sach thu
va kinh » va tinh, qua kinh
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach

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