Perhaps you should try some spelling variations:
a robert » gal robert
robert e » robert _, robert j
a robust » _ robust
heilman » hellman
heilmann » hellmann, heinemann, hermann, hellman
book » books, ebook
heitmann » heinemann, hermann, hartmann
heimann » hermann, heinemann

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. heilman book ) or ( a robust _. (heilmann or (heitmann OR heimann)) book ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( a robert e. heilman book ) OR ( a robust _. (heilmann OR (heitmann OR heimann)) book ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( a robert e. heilman book ) or ( a robust _. (heilmann or (heitmann OR heimann)) book ))*".