I could not find the original reference for the document, either Philips or Intel.

The origin is "MCS 51 Microcontroller Family User's Manual" Order Number 272383-002 February 1994 (I guess there once was a -001, but mine is -002). Copyright INTEL CORPORATION, 1993 (their capitals)

In the initial stages of the development of a "16 bit '51" Intel and Philips were as tight as Ford and Mazda. Philips got to share copyright of the document and did some slight modifications to the format and published it on the web.

Of course, they later had a fallout and Intel made the 'object code compatible' 251 with all the tradeoffs that required. Philips made the much better 'source code compatible' XA with no tradeoffs.

Erik