TODO
(move to DONE below once done)

DONE

  * VN: completeness for holonomic sequences remains open
    * explain in report why I failed to adapt established proofs

  * VN: what's the scope of the method (input format)
    * "- Page 1: "These recurrences have almost the same form as multivariate
      holonomic sequences ..." The exact commonalities and differences are not
      described anywhere in the paper, which would be relevant in order to
      assess the originality of the content in the paper."
    * clarify "sequence term" (Definition)

  * VN/SD(done after operator polynomials to avoid duplicating that):
    * (Not: "Preliminaries" (Sect. 2) on) (holonomic) sequences
    * "Heterogeneous recurrences"

  * JB: Section 2, Inference Rules, should go to report
    and replaced by brief paragraph

  * JB: shorten theory detection

  * JB: Clarify in our examples which ones are not holonomic
  
  * VN/JB: In Summation inference, instead of replacing t≠u by ⋁b⃗∈B {s⃗↦b⃗}(t≠u), we could replace 0≠t[s⃗] by ⋁b⃗∈B 0≠t[b⃗].
    * Reason is, as per reviewer 3, that disjointness of subterms s⃗ is sufficient for their paths: in g(f a)a both f a and a could be generalized simultaneously.

  * VN: "There are claims of a few formulas to be solvable by the procedures
    described in the paper."
    * worked out in appendix why the examples we don't do are solvable,
      NOT simply consequence of holonomic ("this is holonomic because blah ...")
      NOR some other fragment

  * VN (added by jb): Shorten the para starting with "Recurrence equations
    produced by elimination" in the conference version
  
  * VN/SD(not to be done): Fibonacci example: prune the "background" part, to focus on essentials?

  * VN/SD: Explain Sect. 4 material better, more, esp. the excess terms and the
    spine
    * VN/JB: examples of spine

  * VN: "The approach should be qualified relative to prior work on solving
    symbolic summations based on Karr's algorithm for closed form summations,
    http://ftp.gwdg.de/pub/misc/EMIS/journals/SLC/wpapers/s56schneider.pdf
    [Carsten Schneider, 2007]."