Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
tai cua » thai cua, tai cuc, tri cua
va danh » va dinh, va hanh, dia danh
cac dai » cac dan, cac bai, can dai
tu sach » su sach, te sach, tu cach
ty nang » ky nang, ty xang, ty hang
van cac » van hac, van cau, van bac
nang o » nang co, nang ho, nang ro
va dan » ca dan, va dao, va dau
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 ((va danh) OR (va dan)) 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 ((va danh) OR (va dan)) 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 ((va danh) OR (va dan)) tai cua viet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ty nang o hoi. hieu van cac dai ((va danh) OR (va dan)) tai cua viet*.