Among the teachers at Kiel who had a profound influence on him was Landsberg who suggested the topics which were to form Nielsen's doctoral thesis, although Landsberg died before the thesis was completed.
Sa hanay ng mga guro sa Kiel nagkaroon ng malalim na impluwensya sa kanya ay Landsberg sino nagmungkahi ang mga paksa na kung saan ay sa form Nielsen's ng doktor tisis, bagaman Landsberg namatay bago ang tesis ay nakumpleto.