THE HAGUE (Reuters) - Lawyers representing Slobodan Milosevic have asked the U.N. war crimes tribunal to issue a subpoena to force former U.S. President Bill Clinton to testify at his trial, documents showed on Tuesday. "In his position as former president of the United States, Mr Clinton had a continuous role and unique knowledge of events relevant to the indictment," the lawyers said in a written request filed last week but only made public on Tuesday. Lawyers Steven Kay and Gillian Higgins said his evidence was needed to make sure the trial was "informed and fair". They said Milosevic had...