We found this circuit in a 1965 magazine. The circuit can be assembled with current equivalent transistors and the precision in generating the frequencies depends on the tolerance of the capacitors.
This traditional configuration is from a 1976 publication, showing that nothing has changed since...
This circuit was found in an 80's EDN. The circuit uses a current common CMOS, the 4093 powering...
This circuit was obtained in a1969 magazine. The magazine no longer exists, but the circuit can be...