Inscription: Photographer's stamp in ink on print, verso LC: "THE FOLLOWING CREDIT LINE MUST BE USED: // KARSH, OTTAWA"; inscribed in pencil on print, verso LC: "Dr. Alfred Blalock"
Yousuf Karsh, via Jo Tartt
Karsh, Yousuf. Portraits of Greatness. New York: Thomas Nelson and Sons, Ltd., 1959. p. 27.