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2. W. G. Matheson, ‘User Microprogrammability in the HP-21MX Minicomputer,’ Seventh Annual Workshop on Microprogramming Preprints, ACM, September 1974, pages 168–177.
3. ‘21MX Computer Series Reference Manual,’ Manual Part No. 02108–90002, May 1974
4. ‘Microprogamming 21MX Computers Operating and Reference Manual,’ Manual Part No. 02108–90008, August 1974.
5. ‘Emulation - the Key to Computer Power,’;Swain;Canadian Consulting Engineer,1973