Perhaps you should try some spelling variations:
"a robert b. hellman book" » "a robert b. hellman joel", "a robert b. german book", "3 robert b. hellman book", "dr robert b. hellman book", "a robust b. hellman book", "a robert _. hellman book", "a robert e. hellman book", "a robert a. hellman book"
"a robert j. hellman book" » "a robert j. hellman joel", "a robert j. german book", "3 robert j. hellman book", "dr robert j. hellman book", "a robust j. hellman book", "a robert _. hellman book", "a robert e. hellman book"
"_ robust b. heilmann book" » "_ robust _. heilmann book", "_ robust a. heilmann book", "_ robust job. heilmann book", "_ robust b. heilemann book", "_ robust b. heimann book", "_ robust b. heitmann book"

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• Performing a fuzzy search may retrieve terms with similar spellings: (("_ robust b. heilmann book") or ((("a robert b. hellman book") OR ("a robert j. hellman book"))))~.
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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"_ robust b. heilmann book\") or (((\"a robert b. hellman book\") OR (\"a robert j. hellman book\"))))".
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• Adding a wildcard symbol may retrieve word variants: (("_ robust b. heilmann book") or ((("a robert b. hellman book") OR ("a robert j. hellman book"))))*.