Perhaps you should try some spelling variations:
gail robert » gal robert, hall robert, ball robert
robert e » robert _, robert j
a robust » _ robust
robust e » robust _, robust a, robust end
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 ( a robust e. heilmann ebooks ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( gail robert e. heitmann book ) OR ( a robust e. heilmann ebooks ))".
• Adding a wildcard symbol may retrieve word variants: (( gail robert e. heitmann book ) OR ( a robust e. heilmann ebooks ))*.