Jeremy in, "Spies and Spymasters of the Civil War", Markle pub.1994 page 208 under listings of known spies Overall,Mary-CSA sister spyteam in Tenn.Under that Overall,Sophia-CSA sister spy team in Tenn.I think that is the only mention.The bibliography might help for more research. Markle was a Defence Dept.Intelligence Veteran of 34 yrs.