See this legally free ebook:

  • The Doctrine of the Communion of Saints in the Ancient Churcha Study in the History of Dogma, by Dr. J.P. Kirsch, translated with the author’s permission by John R. M’Kee of the Oratory (Edinburgh, London: Sands & Company, 1910). With Imprimatur. Available in various formats at Open Library and Internet Archive, with a second copy at Internet Archive and Open Library.

On the Feast of All Saints in the Latin Church (Roman Rite), the Syro-Malabar Catholic church, and the Maronite Catholic church.