Great Moravia also became a prominent theme of the Czech and Slovak romantic nationalism of the 19th century. The Byzantine double-cross thought to have been brought by Cyril and Methodius is currently part of the symbol of Slovakia and the Constitution of Slovakia refers to Great Moravia in its preamble. Interest about that period rose as a result of the national revival in the 19th century. Great Moravian history has been regarded as a cultural root of several Slavic nations in Central Europe and it was employed in attempts to create a single Czechoslovak identity in the 20th century.