Perhaps you should try some spelling variations:
goal robert » gal robert, goal poverty
robert e » robert _, robert j
a robust » _ robust
heitmann » heimann, hermann
hartmann » hermann
book » books, ebook
eeebooks » eeebookss, eeeebooks
ebooks » ebookss, eebooks

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( goal robert e. (heitmann OR hartmann) book ) OR ( a robust _. heinemann (eeebooks OR ebooks) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( goal robert e. (heitmann or hartmann) book ) or ( a robust _. heinemann (eeebooks OR ebooks) ))~".
• Adding a wildcard symbol may retrieve word variants: (( goal robert e. (heitmann or hartmann) book ) or ( a robust _. heinemann (eeebooks OR ebooks) ))*.