The PDF itself was created in 2005 and the file date in the parent directory the same date as the PDF, so that's the absolute latest date, but I'd also guess 19

The PDF itself was created in 2005 and the file date in the parent directory the same date as the PDF, so that's the absolute latest date, but I'd also guess 1999 for the original paper. Not sticking a date on it without a bit more certainty, though.