Poland (1980-91) - Underground "Solidarity" - Two souvenir sheets commemorating four young people (age 13-20) killed by police forces during workers uprisings.

NSZZ Solidarnosc (NSZZ Solidarity) was an independent  trade union founded by workers in September 1980. The organization was delegalized by the Polish government in December 1981, went underground joining several other underground anti-communist organizations, and reemerged in 1989 to participate in the first free government election in Poland since the 1940s. The name "Solidarity stamps" refers to all post stamps issued by various underground organizations in years 1980-1991.