Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
thu sach » thuat sach, thuoc sach, thu hoach
dai cuu » dai cua, dai huu
dai ban » dai han, tai ban, di ban
bac dai » bach mai
van bac » van ban, van bao, van hac
tu sach » su sach, te sach, tu cach
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
x hoi » o hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (thu sach)) y nang ((x hoi) or (xa hoi)). hieu van bac dai ban thanh dai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) y nang ((x hoi) OR (xa hoi)). hieu van bac dai ban thanh dai cuu tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) y nang ((x hoi) or (xa hoi)). hieu van bac dai ban thanh dai cuu tre*.