Dr. May is included in most lists I have seen. Kees did a tremendous amount of research and included him
here. Fred Hatch, in the December 2003
Journal of the Lincoln Assassination, wrote an article titled "Lincoln's Doctors," and he included May as being at the Petersen House. Dr. Ed Steers lists all the Petersen House doctors in his assassination encyclopedia; Dr. May is in Dr. Steers' list.
However, in
A. Lincoln: His Last 24 Hours, author W. Emerson Reck makes no mention of Dr. May arriving at the Petersen House.
In
American Brutus Mike Kauffman mentions Dr. May was present at the Petersen House, and the footnote reads, "Dr. May's presence at the deathbed is previously unknown, but Dr. Charles Taft's notebook lists him among those who were there."
However, I checked what I thought was Dr. Taft's
notebook, but I cannot find a reference to Dr. May.