(ref.doc)toplas19-2

ACM Transactions on Programming Languages and Systems
March 1997

p 223 Pure versus Impure Lisp
by Nicholas Pippenger
  [Is] impure Lisp [...] "more powerful" than pure Lisp[?]
  The term "pure" goes back to McCarthy et al. [1962]
  [...] it is this representation -rather than the answer- that is
  beyond the power of pure Lisp.
  [redirecting the attention from representations to answers and
  concluding that they are equivalent in power] ignores the issue of
  efficiency.
  [...] we redirect our attention from computability theory to
  complexity theory [...]

p 292 Protocol Specifications and Component Adaptors
by Daniel M. Yellin and Robert E. Strom
  augmentation of application interfaces with enhanced specifications
  the finite-state machines describing the protocols
  software adaptors