Ukraine's president signed a bill Monday dropping his nation's nonaligned status but signaled that he will hold a referendum before seeking NATO membership. Using a news conference to sign the legislation, which parliament had adopted last week, Petro Poroshenko vowed to reform Ukraine's economy and military forces to meet European Union and NATO standards. But he also said he will leave it up to Ukrainian citizens to decide in a popular vote whether to join NATO or not. "When we are able to conform to these criteria, the people of Ukraine will make up their mind about the membership," Poroshenko...