carl47:
However in the MIT core I could only find
Alessandro marked only the files he modified (pins_arduino.c, pins_arduino.h, WInterrupts.c, etcetera) (A.Saporetti and Saposoft).
The core which I use comes from the site you list
His credit is also in that core in the same places.
I do need to apologize. In my mind, it is Alessandro's core because he is responsible for getting it to work on the ATtinyX5 processors. The reality is that the core is the product of many people (including, of course, David Mellis). It is a shining example of what open source is meant to be. So, I apologize to David Mellis and Hernando Barragan. By emphasizing Alessandro's contribution I did not mean to diminish your contributions.