1) en.wikipedia.org/wiki/Calvin_Coolidge

2) www.whitehouse.gov › About the White House

3) millercenter.org/president/coolidge

4) www.calvin–coolidge.org/

5) www.history.com/topics/calvin–coolidge

6) www.brainyquote.com/quotes/authors/c/calvin_coolidge.html

7) www.forbeslibrary.org/coolidge/coolidge.shtml

8) www.britannica.com/EBchecked/topic/136173/Calvin–Coolidge

9) www.ipl.org/div/potus/ccoolidge.html

10) www.pbs.org/wgbh/americanexperience/…/presidents-coolidge/