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

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

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