The US and the European Union have imposed economic sanctions against individual Russian and Ukrainian leaders after yesterday's referendum in Crimea. As if to demonstrate calm and confidence, Vladimir Putin stayed in Sochi for last night's closing ceremonies of the Paralympic Games, where Russian athletes won 80 medals with Ukrainians next with just 25. Elsewhere in Crimea, there was widespread jubilation over yesterday's vote on leaving Ukraine to re-join Russia. But the world is waiting for his next move. Annexing Crimea would be no easy task. Has he gone too far to turn back? Will the West up the ante at great cost to Europe's economy? We look at the options available to both sides and the potential consequences.