Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
va thanh » gia thanh, ban thanh, va tinh
thanh di » thanh doi, thanh de, thanh do
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
v lang » va lang, o lang, van lang
_ lang » o lang, _ land

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((v lang) OR (_ lang)) xa hoi. hieu va cac duc va thanh di ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((v lang) OR (_ lang)) xa hoi. hieu va cac duc va thanh di ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((v lang) OR (_ lang)) xa hoi. hieu va cac duc va thanh di ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: toc sach ((v lang) OR (_ lang)) xa hoi. hieu va cac duc va thanh di ((cua tre) or (cuu tre))*.