Perhaps you should try some spelling variations:
robert b » robert _, robert j, robert a
robert e » robert _, robert j
a robust » _ robust
gal » goal, gael, gail
heitmann » heinemann, hermann, hartmann
eebookss » ebooks, eebooksss, eeebookss
heimann » hermann, heinemann
book » books, ebook

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

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