A new journal issue published today carries this paper: Diomidis Spinellis and Paris Avgeriou Evolution of the Unix System Architecture: An Exploratory Case Study IEEE Transactions on Software Engineering 47(6) 1134--1163 June 2021 https://doi.org/10.1109/TSE.2019.2892149 A preprint is available here: https://www.researchgate.net/publication/332826685_Evolution_of_the_Unix_Sy… However, it is dated four years ago, and after removing its cover page, diffpdf shows numerous changes compared to today's publication. In the new version, a footnote on the first page says Manuscript received 19 May 2018; revised 18 Dec. 2018; accepted 28 Dec. 2018. Date of publication 2 May 2019; date of current version 14 June 2021. ------------------------------------------------------------------------------- - Nelson H. F. Beebe Tel: +1 801 581 5254 - - University of Utah FAX: +1 801 581 4148 - - Department of Mathematics, 110 LCB Internet e-mail: beebe(a)math.utah.edu - - 155 S 1400 E RM 233 beebe(a)acm.org beebe(a)computer.org - - Salt Lake City, UT 84112-0090, USA URL: http://www.math.utah.edu/~beebe/ - -------------------------------------------------------------------------------