public static List<string> NormalizeUrls(List<string> urls, string rootUrl)
{
	Uri uri;
	if (!Uri.TryCreate(rootUrl, UriKind.Absolute, out uri)) return new List<string>();
	return urls.Select(url => !Uri.IsWellFormedUriString(
		url, UriKind.Absolute) ? 
		string.Concat(uri.AbsoluteUri, url) : url).Distinct().ToList();
}