See this online text:
- Encyclical “Paenitentiam Agere” on the Need for the Practice of Interior and Exterior Penance, by Pope John XXIII, July 1, 1962. May be read online on this page of Catholic Culture, on this page of the EWTN Library, and the Holy See. May be read online, and available in mobi and epub formats, at Papal Enyclicals Online. The 1962 edition published by the National Catholic Welfare Conference is available at Open Library.
On Ash Wednesday, 2020 AD, in the Roman Rite. For other online texts and legally free ebooks, you may access the List of Free eBooks (Arranged by Title) and the List of Free eBooks (Grouped by Subject).