Perhaps you should try some spelling variations:
thanh toan » thanh hoa, thanh san, tinh toan
thanh van » thanh san, thanh phan, thanh nhan
dieu tra » dieu tri, kiem tra, dieu cua
so sach » so sanh, bo sach, co sach
cac toc » cac toi, cac nuoc, cac thoi
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
cac tuc » cac tu, cac tac, cac nuoc
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty lang xa hoi. dieu tra ((cac tuc) OR (cac toc)) va ((thanh toan) or (thanh van)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty lang xa hoi. dieu tra ((cac tuc) OR (cac toc)) va ((thanh toan) OR (thanh van)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty lang xa hoi. dieu tra ((cac tuc) OR (cac toc)) va ((thanh toan) or (thanh van)) cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ty lang xa hoi. dieu tra ((cac tuc) OR (cac toc)) va ((thanh toan) or (thanh van)) cua tre*.