“…It was Krylov who initiated the study of linear mappings on generalized matrix algebras from the classifying point of view [34]. Since then many articles are devoted to this topic, and a number of interesting results are obtained (see [1], [3], [6], [7], [12], [19], [23], [24], [40], [41], [42], [60], [61], [62]). Nevertheless, it leaves so much to be desired.…”