In response to a question on February 28, 2011, Dan Van Haften orally demarcarcated the Gettysburg Address in the last 90 seconds of a one hour Extension 720 interview/discussion with Milt Rosenberg on WGN:

The Gettysburg Address starts out with the given: “Four score and seven years ago …” The sought from the enunciation is “testing whether that nation, or any nation so conceived and so dedicated, can long endure.”  And then the exposition:  “We are met on a great battle-field of that war.” The specification  restates more precisely the sought from the enunciation: “We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live.” So the whole point of the Gettysburg Address is that the nation might live.  And then he goes through a construction, and in the proof Lincoln states what we need to do to make the nation live: “[1] “… to be dedicated here to the unfinished work…” [2] “…to be here dedicated to the great task remaining before us…” [3] “…take increased devotion to that cause  and [4] “… highly resolve that these dead shall not have died in vain—.” In the conclusion Lincoln reverts to the sought from the enunciation, stating “that this nation, under God, shall have a new birth of freedom—and that government of the people, by the people, for the people, shall not perish from the earth.” The key phrase there is that this nation shall not perish from the earth.