Perhaps you should try some spelling variations:
gail robert » gal robert, hall robert, ball robert
robert e » robert _, robert j
robust e » robust _, robust end, robust l1
robust a » robust _, robust cat, robust lca
book » books, ebook
ebooks » ebookss, eebooks, books, ebook, redbooks
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) OR (robust a)). heilmann ebooks ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( gail robert e. heitmann book ) OR ( _ ((robust e) OR (robust a)). heilmann ebooks )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( gail robert e. heitmann book ) or ( _ ((robust e) OR (robust a)). heilmann ebooks ))".
• Adding a wildcard symbol may retrieve word variants: (( gail robert e. heitmann book ) or ( _ ((robust e) OR (robust a)). heilmann ebooks ))*.