Benteen's Scout-To-The-Left, the Route from the Divide to the Morass\June 25, 1876 (Custer Trails Series, Vol 1)
The late John Gray, author of Centennial Campaign says, "The route for Benteen's scout from the separation point to reaching Reno Creek, which he (Darling) marked out by superb field work, is by far the best ever and probably definitive.  The writing is clear and coherent and so is easily followed.  Darling's analysis of of Benteen's attitude and frame of mind are not only useful, but judicious, insightful, and non-partisan, because he first nailed down the mechanical details and problems individually, before judging each decision Benteen made. This is unusual indeed."