Perhaps you should try some spelling variations:
"arthur robert van hippel" » "arthur robert v hippel", "arthur robert von hippel", "arthur robert van poppel", "arthur robert van impel"
"arthur robert van koppen" » "arthur robert v koppen", "arthur robert van kampen", "arthur robert van kempen", "arthur robert van kooten"

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 van hippel") OR ("arthur robert van koppen")).
• Removing quotes may allow a broader search: (( arthur robert van hippel ) or ( arthur robert van koppen )).
• Adding a wildcard symbol may retrieve word variants: (("arthur robert van hippel") or ("arthur robert van koppen"))*.