Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sau benh » san benh, phau benh, tai benh
quoc sau » quoc su, quoc suu, quoc sach
nay quoc » nam quoc, nhap quoc, nhan quoc
benh va » benh ve, benh dai, benh tai
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va
song xa » song cua
c song » _ song, k song, cua song
va cua » va chua, via cua, ca cua

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)) c song xa hoi. ((hieu va) OR (hieu qua)) nay quoc sau benh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) c song xa hoi. ((hieu va) OR (hieu qua)) nay quoc sau benh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) c song xa hoi. ((hieu va) OR (hieu qua)) nay quoc sau benh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) c song xa hoi. ((hieu va) OR (hieu qua)) nay quoc sau benh va cua tre*.