I affirm the recommendation for Toni Samek's book Intellectual freedom and social responsibility in American librarianship, 1967-1974 and her more recent Librarianship and human rights : a twenty-first century guide. You might check out Shinjoung Yeo's annotated Alternative Libraries and Infoshops list for leads, especially the bibliography developed by Cherie Yanek at the bottom.

There's a book predating Samek's that she cites several times. I can't remember the title offhand, but it'll be in the notes repeatedly.

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