APA (7 ম সংস্করণ) উদ্ধৃতি

Leffler, G. L. (1949). Average prices of gas, water and electric light and power companies in Pennsylvania since 1939.

শিকাগো স্টাইল (17 তম সংস্করণ) উদ্ধৃতি

Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. State College, Pa, 1949.

M.L.A (8 ম সংস্করণ) উদ্ধৃতি

Leffler, George Leland. Average Prices of Gas, Water and Electric Light and Power Companies in Pennsylvania Since 1939. 1949.