Pletcher, pp. 109–110. The phrase "wise and masterly inactivity", which Calhoun used more than once, originated with Sir James Mackintosh. (source)
dom.edu
listserv.dom.edu
Both Pletcher (p. 223) and Rosenboom (p. 132) note that the slogan was not used in the election. Pletcher also notes that many textbooks get this wrong. See also E.A. Miles, "Fifty-Four Forty or Fight": an American Political Legend, Mississippi Valley Historical Review 44(2), September 1957, pp. 291–309, and Hans Sperber, "Fifty-four Forty or Fight": Facts and Fictions, American Speech 32(1), February 1957, pp. 5–11.
endoftheoregontrail.org
Ewing Young Route. compiled by Karen Bassett, Jim Renner, and Joyce White.
google.co.jp
books.google.co.jp
Mackie, Richard Somerset (1997). Trading Beyond the Mountains: The British Fur Trade on the Pacific 1793-1843. Vancouver: University of British Columbia (UBC) Press. pp. pp. 29, 124-126, 140. ISBN0-7748-0613-3 online at Google Books