def default_key
      k = names[0]
      k = k.respond_to?(:family) ? k.family : k.to_s
      k = BibTeX.transliterate(k).gsub(/["']/, '')
      k = k[/[A-Za-z-]+/] || 'unknown'
      k << (year.to_s[/\d+/] || '-')
      k << 'a'
      k.downcase!
      k
    end
def default_key
      k = names[0]
      k = k.respond_to?(:family) ? k.family : k.to_s
      k = BibTeX.transliterate(k).gsub(/["']/, '')
      k = k[/[A-Za-z-]+/] || 'unknown'
      k << (year.to_s[/\d+/] || '-')
      k << 'a'
      k.downcase!
      k
    end
Returns a default key for this entry.