Perhaps you should try some spelling variations:
van nang » van quang, van ban, van dung
dau ngoc » dau nuoc, dang ngoc, doan ngoc
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
dau xua » dau cua, dao xuan, dau luan
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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 ((van nang) OR (van dong)) xa hoi. hieu va ((dau ngoc) or (dau xua)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((van nang) OR (van dong)) xa hoi. hieu va ((dau ngoc) OR (dau xua)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((van nang) OR (van dong)) xa hoi. hieu va ((dau ngoc) or (dau xua)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((van nang) OR (van dong)) xa hoi. hieu va ((dau ngoc) or (dau xua)) van hanh vi cua tre*.