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.

Complementary Transistor Oscillator (CB495)
Audio signals can be produced by this circuit. Frequency range is determined by C1 and adjusted by...
10 to 84 MHz Colpitts oscillator (CB4052E)
This Colpitts crystal oscillator was found in an American publication for amateurs in the 1980s....
Negative Resistance Circuit (CB926E)
This configuration presents a negative resistance caracteristic such as the one found in...