public override string[] Extract(string html)
        {
            var allLinks = base.Extract(html);
            var retVals  = new List <string>();

            foreach (var link in allLinks)
            {
                if (UrlStandardiser.IsRelative(link) || UrlStandardiser.SameDomain(link))
                {
                    retVals.Add(link);
                }
                else
                {
                    Console.WriteLine("Different domain: " + link);
                }
            }
            return(retVals.Select(UrlStandardiser.Standardise).Distinct().ToArray());
        }