Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
duoc may » duoc ma, hoc may, duoc lam
so sach » so sanh, bo sach, co sach
tinh va » tich va, trinh van, trinh vat
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca 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) or (hoc sach)) ky nang x hoi. hieu van nam ((duoc may) OR (duoc ly)) tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (hoc sach)) ky nang x hoi. hieu van nam ((duoc may) OR (duoc ly)) tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) or (hoc sach)) ky nang x hoi. hieu van nam ((duoc may) OR (duoc ly)) tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((so sach) or (hoc sach)) ky nang x hoi. hieu van nam ((duoc may) OR (duoc ly)) tinh va cua tre*.