Perhaps you should try some spelling variations:
"arthur robert von hippel" » "arthur robert v hippel", "arthur robertson von hippel", "arthur robert vyner hippel"
"arthur robert van poppel" » "arthur robert v poppel", "arthur robert van koppen", "arthur robert van gompel", "arthur robert von popper"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("arthur robert von hippel") OR ("arthur robert van poppel")).
• Removing quotes may allow a broader search: (( arthur robert von hippel ) or ( arthur robert van poppel )).
• Adding a wildcard symbol may retrieve word variants: (("arthur robert von hippel") or ("arthur robert van poppel"))*.