Social Security Administration
Medicare & You 2020 Handbook
https://www.medicare.gov/Pubs/pdf/10050-medicare-and-you.pdf
The Official U.S Government site for Medicare
Choosing a Medigap Policy
https://www.medicare.gov/Pubs/pdf/02110-medicare-medigap-guide.pdf
Medicare Rights Center
https://www.medicarerights.org
Center for Medicare Advocacy