STALIN Archive English on the capitalist crisis http://ciml.250x.com/archive/5classics/english/stalin_crisis/stalin_crisis.html
Lenin: 276. TO THE EDITORIAL BOARDS OF PRAVDA AND IZVESTIA https://www.marxists.org/archive/lenin/works/1921/may/09ebpi.htm
Letters: Karl Marx and Frederick Engels, Selected Correspondence 1884 http://hiaw.org/defcon6/works/1884/letters/84_05_23.html
The Anniversary of the Polish Revolution of 1830 by Frederick Engels https://marxistleninists.org/M&E/1847/12/05.htm