mechanics of the Lublin Union or with later relations between two components of the Polish-Lithuanian Commonwealth. During the second half and following his exile from Russia he re-calibrated his works to analysis of national identities in-between Russia and Poland, though he kept working on his opus magnum, the scholarly edition of Lithuanian statutes from the late 16th century. Grand Duchy Except his mid-term treaty on the Tver county in the 16th. century all Lappo's works have been dedicated to the Grand Duchy of Lithuania. Following minor detailed treaties on juridical establishments, published in the 1890s, his first major work was the graduation disseration Великое княжество Литовское за время от заключения Люблинской Унии до смерти Стефана Батория (1901), a legal-political study on the regime of Grand Duchy between 1569 and 1586. It was followed by the PhD thesis Великое княжество Литовское во второй половине XVI столетия (1911), which extended the analysis until the end of the 16th century. A spate of more focused analytical articles followed in the 1910s; they dealt mostly with various aspects of Lithuanian juridical and legal system, usually with regard to eastern voivodships of Vitebsk and Polock. Western borderlands of Russia On exile Lappo's works suffered from limited access to sources and his focus largely shifted to more general approach, exploring political history of Eastern Europe between Moscow/Russia, Grand Duchy of Lithuania and Poland. Западная Россия и её соединение с Польшей в их историческом прошлом (1924) explored Russian-Polish relations against the broad background of the modern era. Происхождение украинской идеологии Новейшего времени (1926) focused on emergent national identities on western Russia's borderlands, while Идея единства русского народа в Юго-Западной Руси в эпоху присоединения Малороссии к Московскому государству (1929) and Россия и славянство (1930) were studies which examined the Slovianophile idea, especially with regard to the Ukrainian territories. However, Lappo's key historiographic contribution is not an own narrative but en extremely competent and detailed monumental edition of the Lithuanian statutes; as Литовский Статут 1588 года it was issued in 4 volumes in Kaunas in the years of 1934–1936. Key concepts The Russian pre-revolutionary historiography, represented by Nikolay Gerasimovich Ustryalov, Mikhail Osipovich Koyalovich, Nikolay Alexeyevich Maksimieyko, Matvey Kuzmich Lyubavskiy and Fedor Ivanovich Leontovich, worked out a fairly definite assessment of the Union of Lublin and later position of the Grand Duchy within the Polish-Lithuanian Commonwealth. It presented the merger as engineered and carried out by the Poles, who enforced