Perhaps you should try some spelling variations:
thanh di » thanh doi, thanh de, thanh do
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nam xua » nam cua, nam mua, nam qua
cua tre » cua te, cuu tre, cua triet
xua va » xuat va, vua va, sua va
di cua » dai cua, doi cua, de cua
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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 ky nang ((((o hoi) or (o hoc))) or (xa hoi)). hieu van nam xua va thanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((((o hoi) OR (o hoc))) OR (xa hoi)). hieu van nam xua va thanh di cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((((o hoi) or (o hoc))) or (xa hoi)). hieu van nam xua va thanh di cua tre*.