Perhaps you should try some spelling variations:
thanh toan » thanh hoa, thanh san, tinh toan
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, ban thanh, va tinh
so sach » so sanh, co sach, hoc sach
bo sach » co sach, hoc sach
ty tang » tay tang, ty xang, ty hang
tang ma » mang may, tang van
van cau » van dau, van hau, van chat
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet

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) OR (bo sach)) ty tang ma hoa. hieu van cau truc va thanh toan ((cua tre) or (cua vat))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (bo sach)) ty tang ma hoa. hieu van cau truc va thanh toan ((cua tre) OR (cua vat)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) OR (bo sach)) ty tang ma hoa. hieu van cau truc va thanh toan ((cua tre) or (cua vat))".
• Adding a wildcard symbol may retrieve word variants: ((so sach) OR (bo sach)) ty tang ma hoa. hieu van cau truc va thanh toan ((cua tre) or (cua vat))*.