Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
thuc day » thuc dan, thuc vat
day hanh » day nhanh, day thanh, dao hanh
va triet » va thiet, va trien, ve triet
tu sach » thu sach, su sach, te sach
co sach » bo sach, cuon sach, hoc sach
hieu ve » hieu van
hieu va » lieu va, hieu qua
x hoi » xa hoi, o hoi, x ho
vi va » vi van, vai va, vu 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) or (co sach)) ky nang x hoi. ((hieu ve) OR (hieu va)) cam thuc day hanh vi va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (co sach)) ky nang x hoi. ((hieu ve) OR (hieu va)) cam thuc day hanh vi va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (co sach)) ky nang x hoi. ((hieu ve) OR (hieu va)) cam thuc day hanh vi va triet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (co sach)) ky nang x hoi. ((hieu ve) OR (hieu va)) cam thuc day hanh vi va triet*.