Perhaps you should try some spelling variations:
hermann ebooks » german books
heimann books » demand books, german books
ball robert » hall robert, bill robert, ballon robert
robert j » robert _, robert e
a robert » 3 robert, dr robert, a robust
robert b » robert _, robert e, robert a

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( ball robert j. heimann books ) or ( a robert b. hermann ebooks ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ball robert j. heimann books ) OR ( a robert b. hermann ebooks ))*.