From The U.S. National Archives and Records Administration’s Center for Legislative Archives

“Students use a veto message and vetoed bill to make a direct connection between the Constitution, the legislative and veto process, and the separation of powers between the legislative and executive branches of government.” The featured documents (Attempted Override of President Richard Nixon’s Veto of S. 518, an Act to Abolish the Offices of the Director and Deputy Director of the Office of Management and Budget, 1973) enable students to gain a greater understanding of the veto process by working with the Constitution’s veto clauses.

Lesson: http://www.archives.gov/legislative/resources/education/veto/

Source

"The Center for Legislative Archives, a part of the National Archives and Records Administration, preserves and makes available to researchers the historical records of the U.S. House of Representatives and the U.S. Senate. Through its public outreach programs, the Center uses these historical records to promote a better understanding of Congress and the history of American representative government."