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