Sixtus II, pope (257-258), followed Stephen I as bishop of Rome in 257, and suffered martyrdom under Valerian in the following year. He restored the relations with the African and Eastern churches which had been broken off by his predecessor on the question of heretical baptism.
... (http://www.constitutional-law.net/general.html) by Professor Joseph E. Magnet, University of Ottawa
Bibliography
Hogg, P. W., Constitutional law of Canada 4th ed. ...