Perhaps you should try some spelling variations:
thanh vinh » thanh binh, thanh tinh, than kinh
hieu van » hieu va, thien van, lieu va
vinh cuu » dinh cuu, sinh cua, dinh cu
tu sach » thu sach, su sach, te sach
ly nang » ky nang, ly hang, ly vang
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, v nang, may nang
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: tu sach ((y nang) OR (ly nang)) x hoi. hieu van nam ((duc va) or (tuc xa)) thanh vinh cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (ly nang)) x hoi. hieu van nam ((duc va) OR (tuc xa)) thanh vinh cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) OR (ly nang)) x hoi. hieu van nam ((duc va) or (tuc xa)) thanh vinh cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) OR (ly nang)) x hoi. hieu van nam ((duc va) or (tuc xa)) thanh vinh cuu tre*.