Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
thu sach » thuat sach, thuoc sach, thu hoach
ty nang » ky nang, ty xang, ty hang
cac dai » cac bai, can dai, bac dai
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tai cuc, tri cua
tu sach » su sach, te sach, tu cach
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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