Perhaps you should try some spelling variations:
hien sach » kien sach, thien hach, chieu sach
dien sach » dien anh
co sach » bo sach, cuon sach, hoc sach
dau vai » dau va, dau hai, dau tai
vai cua » dai cua, hai cua, lai cua
y lang » o lang, tay lang, yen lang
_ lang » o lang, _ land
va dau » va dao
cua cu » cua chu, cua cau, cua su

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ((y lang) or (_ lang)) xa hoi. hieu ((hien sach) OR (dien sach)) nuoc va dau vai cua cu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ((y lang) OR (_ lang)) xa hoi. hieu ((hien sach) OR (dien sach)) nuoc va dau vai cua cu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ((y lang) or (_ lang)) xa hoi. hieu ((hien sach) OR (dien sach)) nuoc va dau vai cua cu*".