Anna M. Cienciala, a specialist in twentieth-century Polish diplomatic history and Katyn, is a retired professor of history at the University of Kansas, Lawrence. Natalia S. Lebedeva, the leading Russian historian of Katyn, is a researcher at the Russian Academy of Sciences, Moscow, who has edited other documents and published articles on Soviet-Polish relations, the Comintern, and other subjects. Wojciech Materski, the leading Polish historian of Soviet/Russian-Polish relations and Katyn, is director of the Institute of Political Studies, Polish Academy of Sciences, Warsaw.