On 27 April 1892, Hedin traveled to Berlin to continue his studies under Ferdinand Freiherr von Richthofen. Beginning of July he went to University of Halle-Wittenberg, Halle, attending lectures by Alfred Kirchhoff. Yet in the same month, he received the degree of "Doctor of Philosophy" with a 28-page dissertation entitled "Personal Observations of Damavand". This dissertation is a summary of one part of his book, "King Oscar's Legation to the Shah of Persia in 1890". Eric Wennerholm remarked on the subject: