Perhaps you should try some spelling variations:
dieu hien » dieu khien, dieu kien, bieu hien
hanh vai » hanh vi, hanh va, hanh tai
van hanh » van thanh, ban hanh, van anh
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cua viet » ca viet, hoa viet, cua vat
dai hoi » dai hoc, dai hai, dai moi
sach ty » sach y, sach tu, sach thu
mai hoi » mai khoi, lai hoi, mai doi
ty nang » ky nang, ty xang, ty hang
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach

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 ty nang ((mai hoi) or (dai hoi)). dieu hien ((cac nuoc) or (cam xuc)) van hanh vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((mai hoi) OR (dai hoi)). dieu hien ((cac nuoc) OR (cam xuc)) van hanh vai cua viet.
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((mai hoi) or (dai hoi)). dieu hien ((cac nuoc) or (cam xuc)) van hanh vai cua viet*.