Perhaps you should try some spelling variations:
thanh di » thanh doi, thanh de, thanh do
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
xuc va » duc va, tuc va, xac va
luc va » duc va, tuc va, loc va
di cua » dai cua, doi cua, de 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: su ((sach ky) or (sach y)) nang x hoi. hieu van nam ((xuc va) OR (luc va)) thanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach y)) nang x hoi. hieu van nam ((xuc va) OR (luc va)) thanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach y)) nang x hoi. hieu van nam ((xuc va) OR (luc va)) thanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach y)) nang x hoi. hieu van nam ((xuc va) OR (luc va)) thanh di cua tre*.