Hi GrandView. I noticed the statement at the bottom of the document mentions page 248 in the Burch book, "A True Story of Chas. W. Quantrell And his Guerrilla Band". I own a First Edition of this book published in 1923. I will transcribe the passage it refers to here:

"...Quantrell differed in some degree from every Guerrilla who was either a comrade or his contemporary. Not superior to Todd in courage and enterprise, nor to Haller, Poole, Jarrette, Younger, Taylor, Anderson, Frank James, Gregg, Lea, Maddox, Dan Vaughn, or Yager, he yet had one peculiar quality which none of these save Gregg, Frank James, Thrailkill, Lea and Younger possessed to the same pre-eminent degree - extraordinary resource and cunning..."

I hope this is helpful.
~Jay Longley