Page "Antipope John XXIII" Paragraph 13

He should not be confused with Pope John XXIII of the twentieth century.

When Angelo Cardinal Roncalli was elected and became Pope John, there was some confusion as to whether he would be John XXIII or John XXIV ; he then declared that he was John XXIII to put this question to rest.

There was no John XX ; for example, Gibbon refers to the antipope John as John XXII.