Perhaps you should try some spelling variations:
"a robust e. heilman book" » "a robust e. german book", "_ robust e. heilman book", "a robust _. heilman book", "a robust a. heilman book", "a robust end. heilman book"
"a robust e. hellman book" » "a robust e. hellman joel", "a robust e. german book", "_ robust e. hellman book", "a robust _. hellman book", "a robust a. hellman book", "a robust end. hellman book"
"a robust e. heilmann book" » "_ robust e. heilmann book", "a robust _. heilmann book", "a robust a. heilmann book", "a robust end. heilmann book", "a robust e. heilemann book", "a robust e. heimann book", "a robust e. heitmann book"

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("a robust e. heilman book") OR ("a robust e. hellman book"))) or ("a robust e. heilmann book"))~.
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• Adding a wildcard symbol may retrieve word variants: (((("a robust e. heilman book") OR ("a robust e. hellman book"))) or ("a robust e. heilmann book"))*.