Many thanks to SWLing Post contributor, Eric McFadden, who shares the following note from the Southgate ARC:
The article Decoding Numbers Stations by Allison McLellan which appears in the November 2019 issue of ARRL’s QST magazine is available for free download
Download the article PDF from
http://www.arrl.org/this-month-in-qstDigital membership of ARRL costs just £40 ($49)
https://www.arrl.org/membership-levels