Dr. Martin Erdmann, "The Triumph of Progressivism", via ChristianResearchService.com
The Christian Research Service has recently begun to host an abridged English version of Dr. Martin Erdmann's three-volume work, Siegeszug des Fortschrittsglaubens : Mystizismus als Nährboden des Amerikanischen Postmillennialism (The Triumph of Progressivism : Mysticism as the Basis of American Postmillennialism). Although Dr. Erdmann's work on the research project is ongoing, this abridgement (itself being updated periodically) offers valuable insights into his work, and is freely available for download at the CRS website.
As they state on their website:
"CRS is privileged to present an abridged English version of a much-needed survey of the secularized model of Progressivism as it relates to Christianity in America. Dr. Erdmann is completing a three-volume thesis on Progressivism written in German. He is making the translation below available for free, which in time will receive further editorial work. However, there is enough information in the 187 pages currently translated to understand the spiritual problem which the civil religion of Progressivism poses and what needs to be done: sincere repentance and wholehearted turning to God (the latter is not stated in the text, but it is implied)."
The PDF can be accessed free of charge via this webpage at CRS.