Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
dang duc » dang quoc, dao duc, dang su
so sach » so sanh, bo sach, co sach
dau duc » dao duc, dau nuoc
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
ly nang » ky nang, ly hang, ly vang
y nang » ky nang, v nang, may 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: so sach ((y nang) OR (ly nang)) x hoi. hieu va ((dau duc) or (dang duc)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((y nang) OR (ly nang)) x hoi. hieu va ((dau duc) OR (dang duc)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((y nang) OR (ly nang)) x hoi. hieu va ((dau duc) or (dang duc)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ((y nang) OR (ly nang)) x hoi. hieu va ((dau duc) or (dang duc)) van hanh vi cua tre*.