Perhaps you should try some spelling variations:
"a robust e. hellman book" » "a robust e. hellman joel", "a robust e. german book", "_ robust e. hellman book", "a robust a. hellman book", "a robust end. hellman book", "a robust l1. hellman book"
"a robust _. hellman book" » "a robust _. hellman joel", "a robust _. german book", "_ robust _. hellman book"
"a robert e. heitmann book" » "3 robert e. heitmann book", "dr robert e. heitmann book", "a robot e. heitmann book", "a robert _. heitmann book", "a robert j. heitmann book"

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