The annexation of Crimea by Russia in March 2014 took place in the aftermath of the Ukrainian Revolution 2014. It was a part of the wider pro-Russian and anti-government unrest across south-eastern Ukraine.
On 23 February pro-Russian and anti-Kiev demonstrations were held in the Crimean city of Sevastopol. On 27 February unmarked Russian troops from Crimean military bases took over the Supreme Council of Crimea, and secured strategic sites across Crimea by early March. In the mean time a pro-Russian deputy Sergey Aksyonov replaced Anatolii Mohyliov as the head of Council of Ministers of Crimea. On 27 February the Supreme Council of Crimea voted to hold a referendum on 25 May, that was later brought forward. The referendum was judged by the Constitutional Court of Ukraine as unconstitutional. Despite this, on 16 March, a referendum on the status of Crimea took place and subsequently the Crimea's independence was declared, while signing the treaty of accession with the Russian Federation took place on 18 March 2014.
Putin addresses Federal Council on Crimea [RT.com]
Full transcript of Putin's address to the parliament in Russian [Kremlin.ru]
British PM statement on President Putin's actions on Crimea [UK Prime Minister's Office]
William Hague's statement to Parliament on Russia's actions in Crimea [UK Foreign Office]
Readout of Obama's call with Merkel regarding Ukraine [The White House]
EU's Ashton Urges Russia to De-Escalate Tension in Crimea [IBTimes UK via YouTube]
Statement by Turkey's Ministry of Foreign Affairs on Crimea referendum and security of Crimean Tatars [Turkish Foreign Ministry]
Resolution "On the Independence of Crimea" - [Verkhovna Rada Autonomous Republic of Crimea]
Press conference of Mikhail Malyshev regarding the results of Crimean referendum. Video. [112.Ukraina]
Gorbachev: "People of Crimea amend Soviet-era mistake" [Inter Fax]. [Original link not working, please check copy at the Internet Archive]
Fact Sheet: Ukraine-Related Sanctions [The White House]
EU adopts restrictive measures against actions threatening Ukraine's territorial integrity[Council of The European Union]
Obama Speaks on Ukraine [The White House via YouTube]
Crimea referendum should not convince anyone [British Foreign Office]
Churkin's speech at U.N. Security Council regarding a resolution on situation in Ukraine [Russian Permanent Mission to UN]
Crimean referendum unlawful [German Federal Government]
Statement from Amnesty International on the human rights situation in Crimea [Amnesty International]
Press release of Crimean Vekhovna Rada on decision to join Russia - in Russian [Verkhovna Rada Autonomous Republic of Crimea]
Russian troops not involved in Belbek airfield block - Black Sea Fleet spokesperson [The Voice of Russia]. Original link not working, please check copy at the Internet Archive.
Crimean speaker Konstantynov recognizes Yanukovych as incumbent president [The Voice of Russia]. Original link not working, please check copy at the Internet Archive.
Crimean parliamentary speaker Vladimir Konstantinov announces May 25 referendum on greater autonomy for Crimea [Vladimir Konstantinov - YouTube]
People of Crimea have right to express their will - Alexei Pushkov, the head of the international affairs committee of the Russian State Duma [The Voice of Russia]. Original link not working, please check copy at the Internet Archive.
Responding to the Situation in Ukraine [The White House]