Perhaps you should try some spelling variations:
gael robert » gal robert, ebel robert, jaef roberto
robert b » robert _, robert e, robert j
a robert » gal robert
a robust » _ robust
heimann » hermann, heinemann
book » books
ebook » ebooks
heitmann » heinemann, hermann, hartmann

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 b. heimann book ) or ( ((a robert) or (a robust)) _. heitmann ebook ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( gael robert b. heimann book ) OR ( ((a robert) OR (a robust)) _. heitmann ebook )).
• Adding a wildcard symbol may retrieve word variants: (( gael robert b. heimann book ) or ( ((a robert) or (a robust)) _. heitmann ebook ))*.