This is of ongoing interest to me. “Beyond dispute,” like “There’s a consensus,” “The debate is over,” (e.g. “global climate crisis”) is a claim often made but not often proved. Can you provide links to sources?
“Can you provide links to sources?”
Here are a few:
http://mindbodypolitic.com/2015/09/03/angela-merkel-stasi-informant/
http://www.dystopiaearth.com/?p=3276
https://www.wsws.org/en/articles/2005/07/cdu1-j08.html
http://www.veteranstoday.com/2011/11/27/is-german-chancellor-angela-merkel-a-former-communist-spy/