This circuit is from a National Semiconductor manual from the 1980s. The integrated circuit is rare today and next to the diagram we have the formula for calculating the components.
This transistorized circuit with germanium transistors was found in a publication from the 1960s....
This is an old circuit, from 1997, when cathode ray kinescopes were still used in televisions. This...
This circuit found in a documentation of the 90s, uses integrated common at the time, but...