Perhaps you should try some spelling variations:
gail robert » gal robert, hall robert, ball robert
robert e » robert _, robert j
_ robust » _ robert
robust e » robust _, robust a, robust end
book » books
ebooks » ebookss
ebook » ebooks
heilmann » heilemann, heimann, heilman

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

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