The estate of convicted Nazi war criminal John Demjanjuk again asked an appeals court to help posthumously restore his US citizenship earlier this week.In a filing Monday, Demjanjuk's estate asked the full 6th US Circuit Court of Appeals in Cincinnati to take up the case. In June, a three-judge panel of the court ruled that Demjanjuk’s US citizenship cannot be posthumously restored and that his death made the case moot.Demjanjuk, a former Ohio autoworker, died in southern Germany on March 17 at the age of 91.The defense said the American government withheld potentially helpful material and said that the full court must take up the matter.The government argued that the earlier defense filings contained no new information in the matter."Over three decades, we have repeatedly rejected Demjanjuk's challenges to the authenticity of the Trawniki card and fraud on the court," the court said last June. Restoration of his citizenship would have enabled his widow to seek Social Security benefits.A Munich court convicted Demjanjuk last year on 28,060 counts of being an accessory to murder at the Sobibor death camp in occupied Poland. Demjanjuk, who maintained that he had been mistaken for someone else, died while his conviction was under appeal.