This screenshot is taken by the scan of p.19 from vol. 10, issue 6 of Index on Censorship magazine, first published on Dec 1, 1981, available for free download from the page of the magazine in Sage Journals. Look there and download the scan (pdf) which includes another letter by Vonnegut provoked by the ‘Slaughterhouse-Five’ consigned to the flames in a school furnace in North Dakota (Drake School Board) in 1973. Literature as encouragement is the Kurt Vonnegut’s response to Index of Censorship’s request for contributions to their 10th anniversary issue.
Maybe this deserves a separated post but I’ll put it here too: What Kurt Vonnegut Can Teach Us About Coping with the Internet by Jena Saxena. Inspired by the same novel, this is a great article about how living today constantly connected and leaving indelible digital breadcrumbs behind us with every thought or experience shared on whatever online platform is out there — adds 4th dimension in a similar way to the Tralfalmadorian.