Re: A letter want to disprove my paper which submitted recently

In article <f5bsg5$c7p$1@xxxxxxxxxxxxxxx>, Rod Howell <rhowell@xxxxxxx> wrote:
He is claiming that Plesnik's proof is for planar graphs in which each
vertex has at most 2 outgoing edges, but arbitrarily many incoming
edges. I haven't been able to track down Plesnik's paper, so I don't
know whether this is the case. Plesnik's title is ambiguous in this regard.

For the benefit of others reading this, Plesnik's paper is:

J. Plesnik, The NP-completeness of the Hamiltonian cycle problem in
planar digraphs with degree bound two, Inform. Process. Lett. 8 (1979),
no. 4, 199-201.

I just looked at this paper in our library, and Plesnik's result, as
correctly reported by Zhu, is that the directed Hamiltonian path problem
remains NP-complete even if we restrict to the class of planar digraphs
in which every vertex has either (a) indegree 1 and outdegree 2, or
(b) indegree 2 and outdegree 1.
--
Tim Chow tchow-at-alum-dot-mit-dot-edu
The range of our projectiles---even ... the artillery---however great, will
never exceed four of those miles of which as many thousand separate us from
the center of the earth. ---Galileo, Dialogues Concerning Two New Sciences
.