Leffler, G. L. (1949). Average prices of gas, water and electric light and power companies in Pennsylvania since 1939.
Chicagoスタイル(17版)引用形式Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. State College, Pa, 1949.
MLA(8版)引用形式Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. 1949.
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