This is pdfTeX, Version 3.141592653-2.6-1.40.25 (TeX Live 2023/Debian) (preloaded format=pdfetex 2024.11.17)  24 NOV 2024 10:04
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 restricted \write18 enabled.
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**\input ./JetCore.txt
(./JetCore.txt
./JetCore.txt:1: Undefined control sequence.
l.1 \documentclass
                  {book}
? 
./JetCore.txt:1: Emergency stop.
l.1 
    
End of file on the terminal!

./JetCore.txt:1:  ==> Fatal error occurred, no output PDF file produced!