When does the church speak infallibly?

Unfehlbar?

Hans Küng

1971

Anthology of the theological writings of J. Michael Reu

Johann Michael Reu

1997

Origins of papal infallibility, 1150-1350

Brian Tierney

1972

A Letter Addressed to His Grace the Duke of Norfolk

John Henry Newman

1875

The primacy of the Apostolic see vindicated

Francis Patrick Kenrick

1848

A letter addressed to His Grace the Duke of Norfolk on occasion of Mr. Gladstone's recent expostulation

John Henry Newman

1875