I once again taken for a long time the CDs off the shelf (pressure of 1985) and realized that
-The surface of the CDs is easily corroded on the data page
has exited -on the data side adhesive
-the CDs are darkened on both sides and that
-on the label side of the outer edge significantly corroded.
How to DVD's sitting in the wrong digipack, recommended I have cleaned here CDs with lukewarm water and mild soap, but some surface changes are not removable. Therefore, it will not only be beaten adhesive.
I could not fully read the CDs for backup. Who this double CD called his own, may check whether it is still running once.