def author_string
      auth = nil
      if authors.size > 0 # Build based on People 
        case authors.size
        when 1
          auth = authors.first.last_name # self.author
        when 2 
          auth = authors.map(&:last_name).join(" & ")
        when 3...100
          auth =  authors[0..-1].map(&:last_name).join(", ") + " & " + authors.last.last_name
        end
      else # Build based on string
        auth = self.author
      end
      auth
    end
def author_string
      auth = nil
      if authors.size > 0 # Build based on People 
        case authors.size
        when 1
          auth = authors.first.last_name # self.author
        when 2 
          auth = authors.map(&:last_name).join(" & ")
        when 3...100
          auth =  authors[0..-1].map(&:last_name).join(", ") + " & " + authors.last.last_name
        end
      else # Build based on string
        auth = self.author
      end
      auth
    end
return [String] an author string