Perhaps you should try some spelling variations:
"a robert b. german book" » "a robert b. german books", "a robert b. german food", "3 robert b. german book", "dr robert b. german book", "a robot b. german book", "a robert _. german book", "a robert e. german book", "a robert j. german book"
"a robust b. heilman book" » "_ robust b. heilman book", "a robust a. heilman book", "a robust job. heilman book", "a robust l1. heilman book"
"a robust _. heilman book" » "_ robust _. heilman book"

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