Perhaps you should try some spelling variations:
"a robert b. hellman book" » "a robert b. hellman joel", "gal robert b. hellman book", "a robert _. hellman book", "a robert e. hellman book", "a robert j. hellman book"
"a robust b. heitmann book" » "_ robust b. heitmann book", "a robust b. heimann book", "a robust b. heinemann book", "a robust b. hermann book"
"a robust _. heilman book" » "_ robust _. heilman book", "a robust _. heilmann book"

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("a robust b. heitmann book") or ("a robust _. heilman book"))) or ("a robert b. hellman book"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("a robust b. heitmann book") OR ("a robust _. heilman book"))) OR ("a robert b. hellman book")).
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• Adding a wildcard symbol may retrieve word variants: (((("a robust b. heitmann book") or ("a robust _. heilman book"))) or ("a robert b. hellman book"))*.