1890-1938 1892-1985 1912-1992 1917-1991 congresses correspondencetrubet͡skoĭ foreigncountries gumilev history ideology intellectuallife internationalrelations learningandscholarship nikolaĭsergeevich petrpetrovich philosophy politicalaspects politicsandgovernment relations slaviclanguages sovietunion suvchinskiĭ николайсергеевич петрпетрович сувчинский трубецкой