Perhaps you should try some spelling variations:
nhap quoc » han quoc, nha nuoc, phap nuoc
nay quoc » nam quoc, nhan quoc, han quoc
te sach » toc sach
benh li » benh ly, benh lo, benh noi
benh vi » benh va, benh ve, kenh vi
cua tre » cua te, cuu tre, cua triet
sach do » sach dao, sach doi, sach de
hieu va » lieu va, hieu qua
song xa » song cua
do song » doi song, do hong, do cong

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