  This addendum adds some comments to a published paper (B. Schroer, Class.
Quantum Grav. 23, (2006) 5227) on area density of localization-entropy. The
setting of holography and localization-entropy is generalized to double cones
and black holes with bifurcate Killing horizons. PACS: 11.10.-z, 11.25.Hf,
04.70.Dy
