Perhaps you should try some spelling variations:
gail robert » gal robert, davis robert, blair robert
robert j » robert _, robert e
a robust » _ robust
robust e » robust _, robert e
heitmann » heimann, heinemann, hermann
book » ebook
books » ebooks
heilmann » heimann, heinemann, hermann

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 j. heitmann book ) or ( a robust e. heilmann books ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( gail robert j. heitmann book ) OR ( a robust e. heilmann books )).
• Adding a wildcard symbol may retrieve word variants: (( gail robert j. heitmann book ) or ( a robust e. heilmann books ))*.