In Brussels, on 26 March 2014, President Obama lied about a referendum being held in Kosovo prior to its secession from Serbia in February 2008. He was trying to justify US support for Kosovo's secession from Serbia at that time, while condemning Russia for supporting Crimea's secession from Ukraine today.
"And Kosovo only left Serbia after a referendum was organized not outside the boundaries of international law, but in careful cooperation with the United Nations and with Kosovo's neighbors."
That is simply untrue: no referendum of any kind was organised in Kosovo to endorse the declaration of independence by the Assembly of Kosovo in February 2008.
Obama told this lie in an attempt to counter the assertion that the recognition of Kosovo as a state independent of Serbia by the US (and most EU states) set a precedent that Russia has followed in recognising the independence of Crimea from Ukraine.
A key difference, he falsely claimed, is that a referendum was held, "organized ... in careful cooperation with the United Nations and with Kosovo's neighbors", as opposed to the referendum organised by the Crimean authorities themselves on 16 March 2014.
The key similarity, which he doesn't mention, is that there was overwhelming popular support for secession in both Kosovo and Crimea (though secession was opposed by a majority in Serbia and Ukraine as a whole). Yet, the US (and most EU states) support Kosovo's secession, but declare Russia's support for Crimea's secession to be an outrageous infringement of international law. That could be considered a double standard.
(A referendum on Kosovo's independence did take place, after the Assembly of Kosovo made a declaration of independence in September 1991. This declaration was endorsed overwhelmingly in the referendum, but at that time the only state to recognise Kosovo's independence was Albania.)
See also my blog Kosovo and Crimea: US/EU Double Standards.