Complex sentence: A dedicated mailing list was created, and two scientific conferences on QED took place, the first one in 1994 at Argonne National Laboratories and the second in 1995 in Warsaw organized by the Mizar group.
Split into simpler sentences: A dedicated mailing list was created, and two scientific conferences on QED took place. The first one took place in 1994 at Argonne National Laboratories and the second in 1995 in Warsaw organized by the Mizar group.