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

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( gail robert b. heimann book ) OR ( a robust _. (heitmann OR hartmann) (ebooks OR books) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( gail robert b. heimann book ) or ( a robust _. (heitmann OR hartmann) (ebooks or books) ))~".
• Adding a wildcard symbol may retrieve word variants: (( gail robert b. heimann book ) or ( a robust _. (heitmann OR hartmann) (ebooks or books) ))*.