A., S., P., William, S.(1980).Economics / Paul A. Samuelson, William Samuelson (Ed.ke-7).:McGraw-Hill International Book Company.
Gaya MLA
Samuelson, Paul, A.., Samuelson, William."Economics / Paul A. Samuelson, William Samuelson".Ed.ke-7:McGraw-Hill International Book Company,1980.Textbook.