This website provides many publications on genetic disorders as well as the ability to locate genetic counselors through their database.
This organization and website provides a clear description of many chromosome disorders including Down syndrome. It was founded by parents and continues to be run by parents who have children with chromosome disorders.
A clear, concise website on Down syndrome inheritence, tests, cause, treatment, and symptoms. The causes section gives a concise description of the excess of chromosome 21 found in people with Down syndrome.
A references specifically dedicated to chromosome 21 and all possible health conditions related to changes on chromosome 21.
The following organizations and websites have general helpful information about Down syndrome.