The April 2018 monthly edition of
Coin World has a nice article on US Doubled Dies.
The main article deals mostly with the well known
Lincoln Cent DD's.
But doubling of dies created with single-squeeze hubbing is also covered.
That started in 1996 and was supposed to eliminate the doubled dies.
There's a explanation of why there continues to be die doubling.
And finally there is an associated article titled
The Basics of Doubled Die Creation.
Lots of questions answered.