Mattie Burkert and Mark Vareschi have written follow up blog posts to their essay in Theatre Journal Volume 68, Issue 4, based on Burkert's recent archival work at the British Library.
https://mattieburkert.com/2017/09/04/archives-numbers-meaning-a-coda/
https://mvareschi.wordpress.com/2017/09/04/archives-numbers-meaning-a-coda/