Cameron calls on EU for 'credible deal' to keep Britain in

By Elizabeth Piper and Kylie MacLellan BRUSSELS (Reuters) - Prime Minister David Cameron called on EU leaders on Thursday to help him settle the question of Europe for a generation by agreeing a "credible" deal he can sell to the British public and stay in the European Union. At 'now or never' talks in Brussels, leaders worked to overcome differences on the most contentious areas of Cameron's renegotiation of Britain's membership deal - demands for financial safeguards and curbs to some benefits