Perhaps you should try some spelling variations:
ebel robert » fimbel robert, wrobel robert, beyer robert
robert e » robert _, robert j
a robust » _ robust
heitmann » heimann, heinemann, hermann
book » books
ebook » ebooks
eeebooks » eeebookss, ebooks
heilman » heilmann, hellman

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( ebel robert e. heitmann (book OR ebook) ) or ( a robust _. heilman (eeebooks or eeebooks) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ebel robert e. heitmann (book OR ebook) ) OR ( a robust _. heilman (eeebooks OR eeebooks) ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ebel robert e. heitmann (book OR ebook) ) or ( a robust _. heilman (eeebooks or eeebooks) ))*".