What is interesting here, is that the other State that participated in the establishment in 1918 of the Kingdom of Serbs, Croats and Slovenes, was the State of Serbs, Croats and Slovenes. The Kingdom of Serbia and the State of Serbs, Croats and Slovenes, a short-lived state formed from the southernmost parts of the Austrian-Hungarian monarchy after its dissolution at the end of the World War I by the resident population of Slovenes, Croats and Serbs, formed the Kingdom of Serbs, Croats and Slovenes which became Yugoslavia. That means, the serbian people west of the Drina, had formed their own state in 1918 regardless of the kingdom of Serbia. In 1991 the constituent serbian people in Bosnia, in Hercegovina, in Dalmatia, in Slavonia, in the Krajina were denied the right to self-determination and the right to form their own state, although they were entiteled to it it by the yugoslav constitution and the fact that they already had their own state in 1918, the state of Serbs, Croats and Slovenes.
http://lazarus.elte.hu/hun/maps/1910/nepek.gif
The ephemeral political entities self-proclaimed by the Serbs on the states where they were but immigrants cannot be the basis for any territorial claims at the expense of the historical rights of their host nations.
The Serb claim that the right to self-determination applied to "peoples" while ignoring that they could only exercise it within the framework of the Republics and Autonomous provinces made no legal or political sense and that is why was soundly rejected by the "international community", which recognized the borders of some of those constituent entities for what they were according to the Constitution: those of "independent and sovereign states".