Given the specificity of the topic, the authors of the PDF document are likely researchers in the field of astrophysics or astronomy. Some possible sources for this document include:
"McCook & Sion" 140 white dwarf (Add filetype:pdf in Google) "Villanova Catalog" page 140 White Dwarf 140 Pdf
White Dwarf issue #140 was published in August 1991 . While official PDFs of vintage issues are generally not sold by Games Workshop, the content is widely indexed and available through community archives. Issue Highlights: White Dwarf #140 Warhammer 40,000 (Rogue Trader era) : Features rules for Chaos Renegades and the introduction of the first Genestealer Cult expansion details. Warhammer Fantasy : Includes the "Castle Drachenfels" scenario and rules for war machines. Space Fleet : Significant coverage of the Space Fleet board game, which was a precursor to Battlefleet Gothic. 'Eavy Metal Given the specificity of the topic, the authors
: A close look at fiction for both Warhammer Fantasy and Warhammer 40,000, including a detailed map of the Empire. Issue Highlights: White Dwarf #140 Warhammer 40,000 (Rogue
The White Dwarf 140 PDF
provide "revisits" of this specific issue, offering a deep dive into the hobby culture of 1991. download link