Perhaps you should try some spelling variations:
gael robert » gal robert, ebel robert, jaef roberto
a robust » _ robust
robust e » robust _, robert e
heitmann » heimann, heinemann, hermann
book » books, ebook
eebooks » eebookss, eeebooks
ebookss » ebooksss, eebookss
eebookss » eebooksss, eeebookss, ebooks

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( gael robert _. heitmann book ) or ( a robust e. heitmann (eebooks or (ebookss OR eebookss)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( gael robert _. heitmann book ) OR ( a robust e. heitmann (eebooks OR (ebookss OR eebookss)) )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( gael robert _. heitmann book ) or ( a robust e. heitmann (eebooks or (ebookss OR eebookss)) ))".
• Adding a wildcard symbol may retrieve word variants: (( gael robert _. heitmann book ) or ( a robust e. heitmann (eebooks or (ebookss OR eebookss)) ))*.