Original sentence: Peter I (;  – 16 August 1921) reigned as the last King of Serbia (1903–1918) and as the first King of the Serbs, Croats and Slovenes (1918–1921)
Edited sentence: Peter I (;  – 16 August 1921) reigned as the last King of Serbia (1903–1918) and as the first King of Yugoslavia (1918–1921)