Perhaps you should try some spelling variations:
nuoc sach » nguoi sach, hoc sach, cuoc cach
nay thuoc » cay thuoc, nam thuoc, na thuoc
doc sach » hoc sach, toc sach, dac sac
cau tren » cu tren, dau tren, ca tren
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
hieu va » lieu va, hieu qua
vai cau » va cau, van cau, vai cac
va dan » ca dan, va dao, va dap
va dau » va dao
va nay » va ngay, va cay

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((doc sach) OR (nuoc sach)) ty lang xa hoi. hieu va nay thuoc ((va dan) or (va dau)) vai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (nuoc sach)) ty lang xa hoi. hieu va nay thuoc ((va dan) OR (va dau)) vai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((doc sach) OR (nuoc sach)) ty lang xa hoi. hieu va nay thuoc ((va dan) or (va dau)) vai cau tren".
• Adding a wildcard symbol may retrieve word variants: ((doc sach) OR (nuoc sach)) ty lang xa hoi. hieu va nay thuoc ((va dan) or (va dau)) vai cau tren*.