Residents of Smederevo, a Serbian industrial city already blanketed by pollution from a Chinese-owned steel mill, are pushing back against plans for a $2.8 billion oil refinery backed by Chinese state-owned companies -- a project negotiated largely out of public view. Nearly two years after the refinery was announced, Serbia's government has refused to release the framework agreement signed with China Energy International Group. Serbia's Energy Ministry told RFE/RL the deal was a "business secret" and disclosing the agreement would interrupt negotiations…