Perhaps you should try some spelling variations:
"a robert a. hartmann book" » "a robert a. hartmann sonke", "a robert a. hartmann von", "3 robert a. hartmann book", "dr robert a. hartmann book", "a robust a. hartmann book", "a robert e. hartmann book"
"a robert j. hartmann book" » "a robert j. hartmann sonke", "a robert j. hartmann von", "3 robert j. hartmann book", "dr robert j. hartmann book", "a robust j. hartmann book", "a robert e. hartmann book"
"a robert _. german book" » "a robert _. german books", "a robert _. german food", "3 robert _. german book", "dr robert _. german book", "a robust _. german book"

Try widening your search to All Fields.

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 a. hartmann book") OR ("a robert j. hartmann book"))) or ("a robert _. german book"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("a robert a. hartmann book") OR ("a robert j. hartmann book"))) OR ("a robert _. german book")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"a robert a. hartmann book\") OR (\"a robert j. hartmann book\"))) or (\"a robert _. german book\"))".
• Removing quotes may allow a broader search: (((( a robert a. hartmann book ) OR ( a robert j. hartmann book ))) or ( a robert _. german book )).
• Adding a wildcard symbol may retrieve word variants: (((("a robert a. hartmann book") OR ("a robert j. hartmann book"))) or ("a robert _. german book"))*.