The first volume contains Masaryk's correspondence with Poles and letters exchanged with Russians and Ukrainians from 1883 to 1917, while the second volume contains Masaryk's correspondence with Russians and Ukrainians in the interwar period. The third volume contains the correspondence that Masaryk exchanged with South Slavs: Slovenes, Croats, Serbs, and members of nations and ethnic groups in Bosnia and Hercegovina, Montenegro, Macedonia, and Bulgaria from the 1890s until 1937.