Perhaps you should try some spelling variations:
thanh duc » thach duc, than duc, thinh duc
van thanh » ban thanh, van tuan
cua viet » ca viet, hoa viet, cua vat
van hanh » ban hanh, van anh, van ban
va thanh » gia thanh, ban thanh, va tinh
hieu va » lieu va, hieu qua
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach
y nang » ky nang, ly nang, v nang
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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