After returning to Germany he completed his habilitation thesis at Hamburg and then obtained a permanent position at Göttingen working with Reidemeister . He wrote in:
Pagkatapos ng pagbabalik sa Alemanya niya natapos ang kanyang habilitation sanaysay sa Hamburg at pagkatapos ay kinuha ng isang permanenteng posisyon sa Gottingen nagtatrabaho sa Reidemeister. He wrote in: