The reader is referred also to Amort, De Origine, progressu, valore ac fructu Indulgentiarum, and to the article “Ablass” in the Kirchen Lexicon of Wetzer and Welte. Also for the English reader to T. L. Green, D.D., Indulgences, Absolutions, and Tax tables, etc. Some of the difficulties which Roman theologians experience in explaining what are called “Plenary Indulgences” are set forth by Dr. Littledale in his Plain Reasons against joining the Church of Rome, in which the matter is discussed in the usual witty, and unscrupulous fashion of that brilliant writer. But while this remark is just, it should also be remarked that after the exaggeration is removed there yet remains a difficulty of the most serious character.