Perhaps you should try some spelling variations:
thanh toan » thanh hoa, thanh san, tinh toan
thanh van » thanh san, thanh phan, thanh nhan
tu sach » thu sach, su sach, te sach
dua ban » dia ban, cua ban, qua ban
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
dai hoa » dai khoa, dai hoc, dai hoi
mai hoa » mai khoa, ma hoa, lai hoa
ky dang » ky nang, ky danh
cua tre » cua te, cuu tre, cua triet
ca dua » cay dua, ca cua, ca da
va ca » va cac, va cao, va cai

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 ky dang ((mai hoa) or (dai hoa)). hieu va ca dua ban ((thanh van) OR (thanh toan)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((mai hoa) OR (dai hoa)). hieu va ca dua ban ((thanh van) OR (thanh toan)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((mai hoa) or (dai hoa)). hieu va ca dua ban ((thanh van) OR (thanh toan)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((mai hoa) or (dai hoa)). hieu va ca dua ban ((thanh van) OR (thanh toan)) cua tre*.