1. Historical Statistics of the United States, pp. 13, 756.
2. Journal Elk Ridge , Maryland Hall of Records, 1496, 5–42–5 (1765).
3. Wright C. D. , “Historical Review of Wages and Prices, 1752–1860,” Massachusetts Bureau of Statistics of Labor, Sixteenth Annual Report, Part IV, Public Document No. 15 (1885), pp. 201–311.
4. Historical Statistics of the United States, p. 181.