For added information about the 16th Mich. Infantry Rgt. and Battery D, 5th U. S. Artillery Rgt. at Little Round Top read Harry W. Pfanz's Gettysburg--The Second Day
For added information about 22nd Mich. Infantry Rgt. at Chickamauga, Ga. read The Battle of Chickamauga This Terrible Sound by Peter Cozzens.

I'm currently re-reading Cozzens and the 22nd Mich. is mentioned extensively for its fighting on Horseshoe Ridge.