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

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

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