Perhaps you should try some spelling variations:
"christian gottlob frage" » "christian gottlieb frage", "christian gotthilf frage", "christian gottlob frege"
"christian gottlob kruger" » "christian gottlieb kruger", "christian gotthilf kruger", "christian gottlob frege", "christian gottlob fauser"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"christian gottlob frage\") OR (\"christian gottlob kruger\"))".
• Removing quotes may allow a broader search: (( christian gottlob frage ) OR ( christian gottlob kruger )).
• Adding a wildcard symbol may retrieve word variants: (("christian gottlob frage") OR ("christian gottlob kruger"))*.