You might be interested in this book. It has 113 listed articles about the 2nd Michigan Cavalry. Some might be letters, some just where the unit was. The articles are hit and miss. It only covers Detroit newspapers and local newspapers might have some letters and such.
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This book lists 7 sources to include 2 memoirs to include Memoir of John Vogel, immigrant and pioneer. Translated by B. G. Ooserbaan and edited by H. S. Lucas. Mich History Magazine XXX (1946). If I looked I believe I have a copy of that Mich History Magazine here at home some place.
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I might have more info if I looked hard enough.