Perhaps you should try some spelling variations:
a robust » _ robust
robust j » robust _, robert j
robert e » robert _, robert j
heilmann » heitmann, hermann, heymann
hellman » helpman
book » books, ebook
ebooks » ebookss, eebooks, books, ebook
heimann » hermann

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( a robust j. ((heilmann or hellman) or heinemann) book ) or ( gal robert e. heimann ebooks ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( a robust j. ((heilmann OR hellman) OR heinemann) book ) OR ( gal robert e. heimann ebooks )).
• Adding a wildcard symbol may retrieve word variants: (( a robust j. ((heilmann or hellman) or heinemann) book ) or ( gal robert e. heimann ebooks ))*.