Crystal oscillator with a 6A6 (T437E)

We found this circuit with the 6A6 double triode in a 1938 Radio Handbook. The power source is not provided.

Test Everything (CB18000E)
This is a multi-component tester with visual indication by LED and polarity selection in the test....
Astable with the 741 (CB13600E)
This circuit is from a 1978 operational amplifier manual. The power supply must be symmetrical, and the...
Sinusoidal Oscillator 741 (CB14904E)
This circuit is stabilized by a thermistor or NTC with a resistance between 2 and 5k. The signal is...