Schmitz (August 2, 2012). “What Everyone Needs To Know About Good, Bad & Bland Links”. searchengineland.com. Third Door Media. April 21, 2017閲覧。 “"Reciprocal links may not help with competitive keyword rankings, but that does not mean you should avoid them when they make sound business sense. What you should definitely avoid are manipulative reciprocal linking schemes like automated link trading programs and three-way links or four-way links."”
