Editing X-machine (section)

=== Analog X Machine (AXM) ===
The earliest variant, the continuous-time ''Analog X-Machine'' (''AXM''), was introduced by Mike Stannett in 1990 as a potentially "super-Turing" model of computation;<ref
  name="Sta90">M. Stannett (1990) 
  'X-machines and the Halting Problem: Building a super-Turing machine'. 
  ''Formal Aspects of Computing'' '''2''', pp. 331-41.</ref>
it is consequently related to work in [[hypercomputation]] theory.<ref
  name="Cop02">B. J. Copeland (2002) 
  'Hypercomputation'. 
  ''Minds and Machines'' '''12''', pp. 461-502.</ref>