def extract_multiple_numbers(str)
      return [] if str == '' || str.nil?
      str.scan(STDNUMPAT_MULTIPLE).flatten.map{ |i| i.gsub(/\-/, '').upcase }
    end
def extract_multiple_numbers(str)
      return [] if str == '' || str.nil?
      str.scan(STDNUMPAT_MULTIPLE).flatten.map{ |i| i.gsub(/\-/, '').upcase }
    end
Extract the most likely looking numbers from the string. This will be each
 string with digits-and-hyphens-and-maybe-a-trailing-X, with the hypens removed
 @param [String] str The string from which to extract the ISBN/ISSNs
 @return [Array] An array of extracted identifiers