1749-1832 1828-1876 1874-1934 20thcentury authors authorsasartists biography correspondence correspondencekeller correspondencekuh criticismandinterpretationkeller emil germany gottfried henri history hubert jannsen johannwolfgangvon journalists keller léonard marteau politicalandsocialviewsgoethe politicalandsocialviewskeller socializationinliterature swiss violinists