Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cham duc » cham soc, pham duy, phan duc
van hanh » van thanh, ban hanh, van anh
hanh dai » hanh tai, hanh dao, vanh dai
cua viet » ca viet, hoa viet, cua vat
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
x hoi » xa hoi, o hoi, x ho
o hai » co hai, so hai, o lai

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