Johnson, S W, Professor (1860). "Examination of Commercial Fertilizer. Phoenix Guano". Transactions of the Connecticut State Agricultural Society, for the Year 1859. Hartford: Connecticut State Agricultural Society: 35. Retrieved May 6, 2010.{{cite journal}}: CS1 maint: multiple names: authors list (link)
cprr.org
Huffman, Wendell (1999). "Railroads Shipped by Sea". Railroad History. Bulletin 180 (Spring, 1999). Westford, Mass.: Railway & Locomotive Historical Society: 7–30. Retrieved March 7, 2010.