Perhaps you should try some spelling variations:
thien hach » thien thanh, hien hanh
hien sach » dien sach, kien sach, chieu sach
hoc sach » hoc sinh, hoc cac, hoc anh
co sach » bo sach, cuon sach
lang xa » lang ha, dang xay, lang van
dau vai » dau va, dau hai, dau tai
vai cua » dai cua, hai cua, lai cua
y lang » o lang, _ lang, tay lang
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) or (hoc sach)) y lang xa hoi. hieu ((hien sach) OR (thien hach)) nuoc va dau vai cua cu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((co sach) OR (hoc sach)) y lang xa hoi. hieu ((hien sach) OR (thien hach)) nuoc va dau vai cua cu*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((co sach) or (hoc sach)) y lang xa hoi. hieu ((hien sach) OR (thien hach)) nuoc va dau vai cua cu*".