Fessenden, Helen. "Economic History : The Great Telegraph Breakthrough of 1866," in Federal Reserve Bank of Richmond. "Second Quarter 2018, Volume 23, Number 2," Econ Focus (Federal Reserve Bank of Richmond) (Second Quarter 2018) : 30-32. https://fraser.stlouisfed.org/title/3941/item/583197/toc/527151 , accessed on March 21, 2023.