https://revueinvariance.pagesperso-orange.fr/
http://www.sinistra.net/lib/app/alfr/alphafr.html
http://www.pcint.org/04_PC/01%20Som%20PC.htm#No_8
http://groupe-communiste-mondial.org/
https://marx-wirklich-studieren.net/marx-engels-werke-als-pdf-zum-download/