Broadband amplitude-stabilized oscillator

In many applications we need oscillators tunable over a considerable frequency range by simple LC circuits with broadly varying dynamic resistances (quality factor Q of the reactances), while insisting on keeping a rather constant amplitude of the A.C. voltage across the LC circuit, or at least of some output voltage (not necessarily of a harmonic waveform) somewhere in the circuit. If we manage to arrange the circuit in such a way that a variable external load will not cause appreciable frequency shifts of the oscillations, it will be felt as a particular benefit. Another particular benefit will be strongly appreciated: if the circuit does not require any taps (inductive or capacitive) or any transformer coupling in the frequency-determining LC circuit. Perhaps even more appreciated will be a possibility to have one side of the LC circuit grounded. The following paper shows a surprisingly simple circuit capable to fulfill these seemingly conflicting requirements, all at the same time.