Can load network Rload=-Rout/3 rule be used for source network impedance?

Many sources mention than after oscillator power build up Rout (real part of output impedance) becomes less negative, so Rload=-Rout/3 value is used to ensure oscillations. What about Rin (real part of input impedance)? Can this principle also be applied at the input of oscillator? I mean can we use Rsource=-Rin/3 instead?

This is for input of oscillator. Not output.

Thank for your reply! Can you give reference to your book?

"RF Circuit Design Theory and Applications, Second Edition" Reinhold Ludwig, Gene Bogdanov
page 475:
So it seems that rule can be used at any port, input or output.

Very famous book on Microwave Engineering.
https://www.amazon.com/Microwave-Eng...s=books&sr=1-3

But I don't have 4th-edition.
I attached excerption from 3rd-edition.

I think so.