^James W. Cortada, "Rise of the knowledge worker, Volume 8 of Resources for the knowledge-based economy", Knowledge Reader Series, Butterworth-Heinemann, 1998, p. 141, ISBN0-7506-7058-4, ISBN978-0-7506-7058-6.
^"Manufactures of the United States in 1860; compiled from the original returns of the eighth census, under the direction of the Secretary of the interior", Publisher: Government Printing Office, Washington, 1865, p. cxcix: "Salt-making was commenced at Salein in 1636, and in 1641 Samuel Winslow was allowed, for 10 years, the exclusive right of making salt in Massachusetts by a new method."