Perhaps you should try some spelling variations:
david robert » davis robert, davies robert, david romer
robert e » robert _, robert j
a robust » _ robust
heilmann » heilemann, heimann, heitmann
book » books, ebook
redbooks » redbookss, redebooks
redbookss » redbooksss, redebookss, redbook
hellman » helpman, heldman

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

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