Leffler, G. L. (1949). Average prices of gas, water and electric light and power companies in Pennsylvania since 1939.
Čikaški stil citiranja (17. izdanje)Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. State College, Pa, 1949.
MLA način citiranja (8. izdanje)Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. 1949.
Upozorenje: Ovi citati možda nisu uvijek 100% točni.