Perhaps you should try some spelling variations:
gail robert » gal robert, davis robert, blair robert
a robust » _ robust
robust e » robust _, robert e
heitmann » heimann, heinemann, hartmann
book » books, ebook
ebooks » ebookss, eebooks, books, ebook
heilmann » heimann, heinemann, hellman

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

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