Ad fontes: problems of studying Petrozavodsk's twinning ties with Finnish cities

The article offers a brief overview of the history of the twinning movement and raises questions about the extent to which the twinning ties between the municipalities of the Republic of Karelia and Finland are studied. Particular attention is paid to the gaps in the study of Petrozavodsk's relations with its Finnish twin cities Varkaus and Joensuu. The authors come to the conclusion that the history of Karelian-Finnish twinning ties is still understudied and offer a review of the source base, primarily documents available in archives of the Republic of Karelia. Thus, the aim of the article is to guide potential researchers of cross-border cooperation history in Karelia and Finland. In the current international context, such studies are highly relevant and important.