text: * Waller, John, "Einstein's Luck: The Truth Behind Some of the Greatest Scientific Discoveries". Oxford University Press, 2003. .
  * Physics paper [https://history.aip.org/history/exhibits/gap/Millikan/Millikan.html#millikan1 On the Elementary Electrical Charge and the Avogadro Constant (extract)] Robert Andrews Millikan at www.aip.org/history, 2003