Perhaps you should try some spelling variations:
"a robert j. german book" » "a robert j. german books", "a robert j. german food", "3 robert j. german book", "a robot j. german book", "a robert _. german book", "a robert e. german book"
"dr robert j. german book" » "dr robert j. german books", "dr robert j. german food", "dr robert _. german book", "dr robert e. german book"
"a robust _. hellman joel" » "_ robust _. hellman joel", "a robust _. helpman joel", "a robust _. heldman joel"

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