The American Association for Klinefelter Syndrome Information and Support (AAKSIS) is a national volunteer association with the mission of education support, research, and understanding of 47 XXY and its variants, collectively known as Klinefelter syndrome.

More in depth condition information for Klinefelter Syndrome is available at the National Institute of Child Health and Human Development.

The cognitive phenotype in Klinefelter syndrome: a review of the literature including genetic and hormonal factors.

The Klinefelter Syndrome Association offers support and information to all affected by, or having an interest in. They have information available which can assist employers, teachers, social workers, and medical professionals

Consumer-friendly information about human genetics from the U.S. National Library of Medicine

Medline Plus Reference for Klinefelter syndrome