I just received in the mail today a reprint of:
Friedrich Büchsel, Christologie des Hebraerbriefs.
The book was originally published in 1922 and is extremely hard to find, so I am glad that this reprint has been made available at a relatively inexpensive price. It is a small book--only 74 pages. The chapter titles are:
The Son of God
The Historical Jesus
The High Priest
Büchsel was professor at the University of Rostock beginning in 1918.