Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
nang doi » nang doc, nang noi, hang doi
doi cua » dai cua, hoi cua
xa nang » da nang, va nang, xa nong
cac tac » cac toc, cac bac, cac dac
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
cac tuc » cac toc, cac tu, cac nuoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ky lang) or (ky tang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) xa nang doi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky lang) OR (ky tang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) xa nang doi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky lang) or (ky tang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) xa nang doi cua viet".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky lang) or (ky tang)) xa hoi. hieu ve ((cac tuc) OR (cac tac)) xa nang doi cua viet*.