In 1901 he presented his doctoral thesis Über Reihen auf der Convergenzgrenze to Erlangen and in the same year it was published in the Philosophical Transactions.
1901 siya sa kanyang ipinapahayag ng doktor ang Über Reihen auf der Convergenzgrenze na Erlangen at sa parehong taon, ito ay nai-publish sa pilosopiko transaksiyon.