Double Pangram Lists
Darryl Francis · Digital Commons @ Butler University (Butler University) · 1978
The November 1971 Kickshaws introduced the problem of finding thirteen four-letter words which together contain each of the 26 letters twice. Leslie Card exhibited a list of fourteen four-letter words, with four extraneous letters. Dave Silverman commented "we don't expect anyone to come up with a 13-word list in the near future" -- and he was right.