Conference of Solidarity Support Organizations
Conference of Solidarity Support Organizations (CSSO) was an international organization of national groups that supported the trade union Solidarność and human rights in Poland during the final years of the Polish People's Republic. Member organizations agreed to the CSSO Letter of Agreement of January 8/9, 1983, and there were eventually more than twenty international chapters.
Source: Wikipedia — Conference of Solidarity Support Organizations (CC BY-SA 4.0)