Complex sentence: In 1989 a group of RC leaders, led by Daniel le Bon, resigned from RC, stating in their resignation letter that RC had no scientific basis and that the process of "discharge" did not work.
Split into simpler sentences: In 1989 a group of RC leaders, led by Daniel le Bon, resigned from RC. In their resignation letter they said that RC had no scientific basis and that the process of "discharge" did not work.