Serb People's Radical Party  The Serbian People's Radical Party (Serbian: Српска народна радикална странка, "Srpska narodna radikalna stranka") was an ethnic Serb political party in Austria-Hungary. It was a sister party of the People's Radical Party in Serbia. It was one of the founders of the Serbo-Croat coalition (1905) that governed the Kingdom of Croatia-Slavonia, but it left the Coalition soon afterwards. In 1918, it had two representatives in the National Council of Slovenes, Croats and Serbs.