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