- The article is online in academia.edu, in archive.org and also here in snrk.de (with permission of the Knight Letter editors). As a bonus, four additional images have been attached to that online version of the article.
- Mahendra Singh’s blog
- Waistcoat Poetry | Martin Gardner and Elizabeth Sewell | MG058 (Martin Gardner’s annotation number)
- Henry Holiday’s Snark Illustrations: in en.wikipedia.org, in chch.ox.ac.uk/library-and-archives and also here in snrk.de
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2017-08-29, update: 2021-05-07