is said to be stable [completely unstable] if all point matrices
are stable [unstable]. If
contains both, stable as well as unstable point matrices then
is called of composite stability type. In the first of the two papers, conditions are established that are sufficient for
to be stable, to be unstable, and to be of composite type. - The second paper is concerned with that special class of interval matrices
. For this special class, necessary and sufficient conditions for
to be stable, to be unstable or to be of composite type are given.