Perhaps you should try some spelling variations:
thanh di » thanh doi, thanh de, thanh do
toc sach » hoc sach, doc sach, thuoc sach
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
ty hang » ly hang, ty xang, thi hang
cua tre » cua te, cuu tre, cua triet
hang x » nang x, hoang xa, chang xu
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: ((te sach) OR (toc sach)) ty hang x hoi. hieu van ((cac duc) or (cac dac)) va thanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ty hang x hoi. hieu van ((cac duc) OR (cac dac)) va thanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ty hang x hoi. hieu van ((cac duc) or (cac dac)) va thanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ty hang x hoi. hieu van ((cac duc) or (cac dac)) va thanh di cua tre*.