Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
ban benh » san benh, ba benh, ban banh
tu sach » su sach, te sach, tu cach
bo benh » so benh, o benh, ba benh
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, x ho

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang x hoi. hieu van pham duc ((ban benh) OR (bo benh)) dai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky nang x hoi. hieu van pham duc ((ban benh) or (bo benh)) dai cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ky nang x hoi. hieu van pham duc ((ban benh) or (bo benh)) dai cua tre*.