Perhaps you should try some spelling variations:
nuoc san » nuoc luan, nguoi san, nuoc quan
lang van » dang van, tang van, hoang van
quoc san » quoc sang, quoc ban, quoc lan
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
benh vi » benh va, benh ve, benh li
van cau » van dau, van hau, van chat
lang xa » lang ha, dang xay
cua tre » cua te, cuu tre, cua triet
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: tu sach y ((lang xa) or (lang van)) hoi. hieu van cau ((quoc san) OR (nuoc san)) benh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((lang xa) OR (lang van)) hoi. hieu van cau ((quoc san) OR (nuoc san)) benh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((lang xa) or (lang van)) hoi. hieu van cau ((quoc san) OR (nuoc san)) benh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((lang xa) or (lang van)) hoi. hieu van cau ((quoc san) OR (nuoc san)) benh vi cua tre*.