This circuit can be used to obtain a zener voltage from a common zener of another value, adjusting in a multimeter. The circuit is from an American documentation of the 1970s.
This configuration using the four transconductance operational amplifiers of an LM3900 was found...
This alarm, from a 1996 magazine, can be fitted with two BC548s in the original configuration...
This circuit was found in a 1973 magazine but can still be assembled using modern equivalent...