Perhaps you should try some spelling variations:
cam thuc » am thuc, cam thu, can thuc
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
vi cua » vai cua, di cua
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y nang x hoi. hieu ve ((cam thuc) OR (nam thuc)) ((va hanh) or (van hanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang x hoi. hieu ve ((cam thuc) OR (nam thuc)) ((va hanh) OR (van hanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang x hoi. hieu ve ((cam thuc) OR (nam thuc)) ((va hanh) or (van hanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach y nang x hoi. hieu ve ((cam thuc) OR (nam thuc)) ((va hanh) or (van hanh)) vi cua tre*.