Original sentence: His career suffered a very significant and irreparable decline in the postwar period, due mainly to a famous letter published by his former teacher Casals in the New York Times accusing him, unfairly, collaborationism with the fascist regimes and asking not to be allowed to play in the allied countries
Edited sentence: His career suffered a very significant and irreparable decline in the postwar period, due mainly to a famous letter published by his former teacher Casals in the New York Times accusing him of collaborationism with the fascist regimes and asking not to be allowed to play in the allied countries