This circuit uses a feedback integrator. We found it in Ferranti's transistor manual from 1974. Transistors are general-purpose types at the time.
We found this circuit in a 70s American documentation. The integrated circuits are from that time....
The integrated circuit used in this regulator is unusual, as are the transistors. The circuit is...
This circuit was found in an old Radio Electronics, but can still be assembled as the components are...