The Budapest Memorandum is a diplomatic agreement from 1994 between Ukraine, Russia, U.K., and U.S. This memo states that the Ukraine would disarm its nuclear arsenal and that, “The Russian Federation, the United Kingdom of Great Britain and Northern Ireland and the United States of America reaffirm their commitment to Ukraine, in accordance with the principles of the Final Act of the Conference on Security and Cooperation in Europe, to respect the independence and sovereignty and the existing borders of Ukraine (Article 1).” There is currently a debate going on whether this article was violated with current action in the Crimea, which has been cited numerous times.
Gilbert, Paul. “Budapest Memorandum December 1994.” Youtube. March 2, 2014. http://www.youtube.com/watch?v=B21IDpsSgZU
Permanent Mission of the Republic of Poland to the United Nations Office and International Organizations in Vienna. “Memorandum on Security Assurance in connection with Ukraine’s accession to the Treaty on NPT.” https://www.msz.gov.pl/en/p/wiedenobwe_at_s_en/news/memorandum_on_security_assurances_in_connection_with_ukraine_s_accession_to_the_treaty_on_the_npt?printMode=true
Radio Free Europe. “Live Blog Ukraine On The Brink.” http://www.rferl.org/contentlive/clashes-in-ukraine-live-blog-kyiv/25267783.html
Synovitz, Ron. “The Budapest Memorandum and Crimea.” VOA. March 2, 2014. http://www.voanews.com/content/the-budapest-memorandum-and-crimea/1862439.html
——. Explainer; The Budapest Memorandum and Its Relevance to Crimea. Radio Free Europe. March 2, 2014. http://www.rferl.org/content/ukraine-explainer-budapest-memorandum/25280502.html
The White House, Office of the Press Secretary. “Readout of President Obama’s Call with President Putin.” March 1, 2014. http://www.whitehouse.gov/the-press-office/2014/03/01/readout-president-obama-s-call-president-putin