def title_part_validate(root)
        title_part_en = root.at("//title[@type='title-part' and @language='en']")
        title_part_zh = root.at("//title[@type='title-part' and @language='zh']")
        if title_part_en.nil? && !title_part_zh.nil?
          @log.add("Style", title_part_en,  "No English Title Part!")