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, bo sach, co sach
ty tang » tay tang, ty xang, ky tang
ty hang » ly hang, ty xang, thi hang
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 ((ty tang) OR (ty hang)) 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 ((ty tang) OR (ty hang)) 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 ((ty tang) OR (ty hang)) ma hoa. hieu van cau truc va thanh toan ((cua tre) or (cua vat))".
• Adding a wildcard symbol may retrieve word variants: so sach ((ty tang) OR (ty hang)) ma hoa. hieu van cau truc va thanh toan ((cua tre) or (cua vat))*.