To Alexander Berkman, 20th November 1908
To De Reijger, 23rd December 1920 (Kropotkin’s Last Letter)
To Editor of Le Soir, 18th February (Published in Bread and Freedom)
To Lenin, 4th March 1920
To Lenin, 21st December 1920
To Marie Goldsmith, 23rd January 1913
To Marie Goldsmith, 23rd February 1916
To Nettlau, 5th March 1902
To Steffen (on WWI)