Björner's example of non-extendably shellable 2-polyhedron

Description

This strange example was made by Björner. This is shellable but not extendably shellable. Identify the vertices with the same labling. That is, this example is made from a projective plane and one additional triangle.

Properties

The smallest example which is shellable but not extendably was found by Moriyama and Takeuchi, with 6 vertices and 9 facets. That this Björner's example has non-zero homology and that it has no boundary should be remarked.

Datum

bjorner.dat

Some table

vertex decomposable?	yes
extendably shellable?	no
shellable?	yes
constructible?	yes
Cohen-Macaulay?	yes
partitionable?	yes
topology	projective plane + one facet
f-vector	(1,6,15,11)
h-vector	(1,3,6,1)
made by	Bjorner