Perhaps you should try some spelling variations:
hermann books » german books, hermann brochs, hermann broch
demand books » hand books, land books
robust b » robust _, robust job, robust l1
robust a » robust _, robust cat, robust lca
a robert » 3 robert, dr robert, a robust
robert e » robert _, robert j

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

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