This undated photo provided by permission of the Houghton Library at Harvard University in Cambridge, Mass., shows one of two pages from the library's archives (call number MS Am 1326) that Illinois State University math professors Nerida Ellerton and Ken Clements on Friday, June 7, 2013 confirmed as two new pages to add to the math notebook believed to be the oldest surviving document written by Abraham Lincoln. The pages are from the 1820s. Lincoln's stepmother gave the notebook to Lincoln law partner William Herndon after the 16th president's death. (AP Photo/With permission of the Houghton Library, Harvard University)