Perhaps you should try some spelling variations:
fogel robert » jovel roberto, fimbel robert, wrobel robert
german book » german books, german food
robert e » robert _, robert j
a robust » _ robust
robust e » robust _, robust a, robust end
heilmann » heilemann, heimann, heitmann
eebooks » ebooks, redbooks, texbooks

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: (( fogel robert e. ((heilman book) OR (german book)) ) OR ( a robust e. heilmann eebooks ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( fogel robert e. ((heilman book) OR (german book)) ) or ( a robust e. heilmann eebooks ))~".
• Adding a wildcard symbol may retrieve word variants: (( fogel robert e. ((heilman book) OR (german book)) ) or ( a robust e. heilmann eebooks ))*.