Problem: Background: Winfrey's first name was spelled "Orpah" on her birth certificate after the biblical figure in the Book of Ruth, but people mispronounced it regularly and "Oprah" stuck. She was born in Kosciusko, Mississippi, to an unmarried teenage mother. She later said that her conception was due to a single sexual encounter and the couple broke up not long after. Her mother, Vernita Lee (born c. 1935), was a housemaid.
Context: In 1993, Winfrey hosted a rare prime-time interview with Michael Jackson, which became the fourth most-watched event in American television history as well as the most watched interview ever, with an audience of 36.5 million. On December 1, 2005, Winfrey appeared on the Late Show with David Letterman to promote the new Broadway musical The Color Purple, of which she was a producer, joining the host for the first time in 16 years. The episode was hailed by some as the "television event of the decade" and helped Letterman attract his largest audience in more than 11 years: 13.45 million viewers. Although a much-rumored feud was said to have been the cause of the rift, both Winfrey and Letterman balked at such talk. "I want you to know, it's really over, whatever you thought was happening", said Winfrey. On September 10, 2007, Letterman made his first appearance on The Oprah Winfrey Show, as its season premiere was filmed in New York City.  In 2006, rappers Ludacris, 50 Cent and Ice Cube criticized Winfrey for what they perceived as an anti-hip hop bias. In an interview with GQ magazine, Ludacris said that Winfrey gave him a "hard time" about his lyrics, and edited comments he made during an appearance on her show with the cast of the film Crash. He also said that he wasn't initially invited on the show with the rest of the cast. Winfrey responded by saying that she is opposed to rap lyrics that "marginalize women", but enjoys some artists, including Kanye West, who appeared on her show. She said she spoke with Ludacris backstage after his appearance to explain her position and said she understood that his music was for entertainment purposes, but that some of his listeners might take it literally. In September 2008, Winfrey received criticism after Matt Drudge of the Drudge Report reported that Winfrey refused to have Sarah Palin on her show, allegedly because of Winfrey's support for Barack Obama. Winfrey denied the report, maintaining that there never was a discussion regarding Palin's appearing on her show. She said that after she made public her support for Obama, she decided that she would not let her show be used as a platform for any of the candidates. Although Obama appeared twice on her show, those appearances were prior to his declaring himself a candidate. Winfrey added that Palin would make a fantastic guest and that she would love to have her on the show after the election, which she did on November 18, 2009.  In 2009, Winfrey was criticized for allowing actress Suzanne Somers to appear on her show to discuss hormone treatments that are not accepted by mainstream medicine. Critics have also suggested that Winfrey is not tough enough when questioning celebrity guests or politicians whom she appears to like. Lisa de Moraes, a media columnist for The Washington Post, stated: "Oprah doesn't do follow-up questions unless you're an author who's embarrassed her by fabricating portions of a supposed memoir she's plugged for her book club."
Question: Did she appear on his show more then once?
Answer: On September 10, 2007, Letterman made his first appearance on The Oprah Winfrey Show, as its season premiere was filmed in New York City.

Problem: Background: Vladimir Tismaneanu (Romanian pronunciation: [vladi'mir tism@'neanu]; born July 4, 1951) is a Romanian and American political scientist, political analyst, sociologist, and professor at the University of Maryland, College Park. A specialist in political systems and comparative politics, he is director of the University of Maryland's Center for the Study of Post-Communist Societies, having served as chairman of the editorial committee (2004-2008) and editor (1998-2004) of the East European Politics and Societies academic review. Over the years, Tismaneanu has been a contributor to several periodicals, including Studia Politica, Journal of Democracy, Sfera Politicii, Revista 22, Evenimentul Zilei, Idei in Dialog and Cotidianul. He has also worked with the international radio stations Radio Free Europe and Deutsche Welle, and authored programs for the Romanian Television Company.
Context: Outside the realms of history, political science and political analysis, Vladimir Tismaneanu is a noted author of memoirs. This part of his work is centered on the volume Ghilotina de scrum ("The Ashen Guillotine"), also written on the basis of interviews with Mihaies. The book offers an account of his complicating relationship with Leonte Tismaneanu, postulating a difference between the everyday father, who has earned his son's admiration for being marginalized by his political adversaries, and a "political father", whose attitudes and public actions are rejected by Vladimir Tismaneanu.  This approach earned praise from two influential intellectual figures of the Romanian diaspora, critics Monica Lovinescu and Virgil Ierunca, whose letter to the author read: "the distances you take from your own background are of most-rare authenticity and tact. You accomplish a radical break, being at the same time participative, negating things only after you have understood them, being dissociated from both roles of judge and defense counsel." Cioroianu also notes: "He is not the only son of (relatively) well-known communists; but he is one of the few to have reached the level of detachment needed in order to X-ray, in a cold and precise way, a political system. Does this seem easy to you? I do not know how many of us would be capable of introspecting with such lucidity our own parents' utopias, phantasms and disappointments". The historian opposes Tismaneanu's approach to that of Petre Roman, Romania-s first post-1989 Premier, whose attempts at discussing the public image of his father, the communist politico Valter Roman, are argued by Cioroianu to have "failed".  Tismaneanu has contributed the screenplay for Dinu Tanase's documentary film Condamnati la fericire ("Sentenced to Happiness"), released in 1992. With Octavian Serban, he has also authored a series about Communist Romania, which was showcased by the Romanian Television Company.
Question: What contributions did he make?
Answer:
Vladimir Tismaneanu is a noted author of memoirs.