Perhaps you should try some spelling variations:
hermann ebooks » german books
goal robert » gal robert, deal robert, fogel robert
robert b » robert _, robert e, robert j
a robust » _ robust
heilmann » heilemann, heimann, heitmann
book » ebook
books » ebooks
ebooks » eebooks

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( goal robert b. heilmann (book or books) ) or ( a robust _. hermann ebooks ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( goal robert b. heilmann (book OR books) ) OR ( a robust _. hermann ebooks )).
• Adding a wildcard symbol may retrieve word variants: (( goal robert b. heilmann (book or books) ) or ( a robust _. hermann ebooks ))*.