Sentence:  From a clandestine network of friends passing to each other typed copies of their new work, the initiative developed over the years into a parallel publishing system. ... [I]n cities the inquisitive reader did not have much difficulty in obtaining access to what was in fact a banned literature. <WSD>Samizdat</WSD> was also an important source of new writing for the equally active and enterprising publishers of Czech (and some Slovak) books in exile. 
Meaning of the word marked with <WSD> tags:  The secret copying and sharing of illegal publications, chiefly in the Soviet Union; underground publishing and its publications. (from 1950s.)