The British folk musician Cat Stevens has postponed his North American tour, delaying his scheduled stop in Philadelphia this week. Stevens, who also goes by Yusuf, said he was putting the tour on hold due to unresolved visa issues. "Waiting months for visa approvals, we held out as long as we could," Stevens wrote on his website and social media accounts. Not least for my fans who have bought tickets and made travel plans to see me perform. North American audiences may still get a chance to see the tour if visa approvals eventually come through.