Since 1957, George Grätzer published nineteen definitive papers in the
Acta Scientiarum Mathematicarum.
In these papers he solved several hard problems and proved many
deep results in universal algebra and lattice theory.
The classical Grätzer--Schmidt Theorem characterizing
congruence lattices of algebras, published here exactly
forty years ago, is worth separate mentioning.
The Medal was presented to George Grätzer at 14:00, May 13, 2004
in the Bolyai Institute.
On this occasion he delivered a lecture ``Nice lattices".