At the ambassadorial conference of Constantinople in 1876 the cazas of Kastoria and Florina were included within the boundaries of the proposed autonomous province which was to have Sofia as its capital. The treaty of San Stefano likewise comprised the districts under the newly created Bulgaria. These considerations suffice in themselves to demonstrate the Bulgarian nationality of the inhabitants of the present northern confines of Greece. The Serbian claim on portions of Macedonia acquired after the Balkan war of 1913 rests largely on a relatively short term of military occupation at the height of the Serbian might in the fourteenth century. This is made the basis of an historical plea. The crowning of Dushan, their most renowned ruler, in the city of Uskub however did not change the national character of the inhabitants of the city or the districts surrounding it. Furthermore, Serbian rule in Macedonia was preceded by Bulgarian sovereignty and was followed by Byzantine supremacy over the land. Greeks and Bulgarians may therefore buttress their claims on equally valid historical contentions. Samuel, one of the Bulgarian Czars, had extended his domain as far west as the Adriatic. His success in adding the seaport of Durazzo to his land, however, failed to change the Serbian nationality of the western districts he managed to conquer. Only in recent years have Serbian claims on Macedonia been set forth by Serbian scholars. Historians like Raitch, Solaritch and Vouk Karadjitch formerly concurred in setting southern Serbian frontiers at the Shar mountains. In 1860 Serbian scientific societies had joined in the publication of Macedonian songs collected by Verkovitch under the title of “Bulgarian Songs.” Serbian writers of the period around 1870 describe inland inhabitants of Thrace, Rumelia and Macedonia as Bulgarians, while they recognized the coast dwellers as Greeks.[199] A transition dialect between Bulgarian and Serbian is spoken by the inhabitants of the Krajste and Vlasina valleys in eastern Serbia. The Krajste, an ill-known region, skirts the Serbo-Bulgarian boundary and spreads eastward to the basins of Tren and Kustendil. The Vlasina upper valley is known to Serbians as containing the most important peat bog in their country. The two districts are characterized by seasonal migrations of their inhabitants which acquire decided intensity in the Vlasina valley.[200]