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 | Calixtus I - Biographical profile of the third-century pope, in the 1911 Encyclopædia Britannica.
|  | Callistus (Callixtus) I, Pope - Biographical portrait.
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 | Callistus I - Illustrated profile, with links.
|  | Callixtus I - Short biography, by Karen Rae Keck. It was Callixtus who excommunicated Sabellius.
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 | Catholic Online: St. Callistus I - Hagiography, by Terry Matz.
|  | Pope Callistus I - Martyr, d. about 223. Also known as Callixtus or Calixtus.
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 | St. Calixtus I - This pope is known mostly through the writings of his enemies.
|  | St Calixtus, or Callistus, Pope, Martyr - From Butler's Lives of the Saints.
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 | Vietnamese Eucharistic Youth Society: St. Callistus I - The story of this pope, suited to children.
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