Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
hanh dai » hanh tai, hanh dao, vanh dai
van hanh » van thanh, ban hanh, van anh
cong cua » cong cu, dong cua, huong cua
cam thuc » nam thuc, cam thu, can thuc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
song xa » song cua
hieu ve » hieu va, hieu van
dai va » mai va

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 ((song xa) or (cong cua)) hoi. hieu ve ((cam thuc) OR (am thuc)) van hanh dai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((song xa) OR (cong cua)) hoi. hieu ve ((cam thuc) OR (am thuc)) van hanh dai va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((song xa) or (cong cua)) hoi. hieu ve ((cam thuc) OR (am thuc)) van hanh dai va triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((song xa) or (cong cua)) hoi. hieu ve ((cam thuc) OR (am thuc)) van hanh dai va triet*.