Perhaps you should try some spelling variations:
"a robert b. german books" » "a robert b. german book", "a robert b. german food", "3 robert b. german books", "a robust b. german books", "a robert _. german books", "a robert j. german books", "a robert a. german books", "a robert b. german ebooks"
"a robot b. german books" » "a robot b. german book", "a robot b. german food", "_ robot b. german books", "a robust b. german books", "a robot _. german books", "a robot 1. german books", "a robot 5. german books", "a robot b. german ebooks"
"dr robert e. heitmann book" » "dr robert _. heitmann book", "dr robert j. heitmann book", "dr robert e. heitmann ebook"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("dr robert e. heitmann book") or ((("a robert b. german books") OR ("a robot b. german books"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("dr robert e. heitmann book") OR ((("a robert b. german books") OR ("a robot b. german books")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"dr robert e. heitmann book\") or (((\"a robert b. german books\") OR (\"a robot b. german books\"))))".
• Removing quotes may allow a broader search: (( dr robert e. heitmann book ) or ((( a robert b. german books ) OR ( a robot b. german books )))).
• Adding a wildcard symbol may retrieve word variants: (("dr robert e. heitmann book") or ((("a robert b. german books") OR ("a robot b. german books"))))*.