Perhaps you should try some spelling variations:
a robert » 3 robert, dr robert, a robust
robert e » robert _, robert j
robust b » robust _, robust job, robust l1
robust a » robust _, robust cat, robust lca
heilmann » heilemann, heimann, heilman
book » books, ebook
ebooks » ebookss, eebooks, books, ebook, redbooks

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

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