Astable Multivibrators
Multivibrator oscillators were invented during the first World War, in the early days of triode vacuum tubes.
The first set of slides below focus on design using bipolar junction transistors.
The second set contains examples with vacuum tube triodes and junction FETs.
The multivibrator topology today is commonly referred to as a cross-coupled (transistor) pair.
Dr. Behzad Razavi has an interesting 3-part paper on the Cross-Coupled Pair. In Part-3, he mentions the historical development of oscillators from the RC multivibrator, to the coupled-cathode (emitter) RC oscillator, to the coupled-cathode (emitter) LC oscillator.
The papers, originally in 2014-2015 issues of IEEE Solid-State Circuits Magazine, are available at Dr. Razavi's web page here .
https://www.seas.ucla.edu/brweb/papers/Journals/BR_Magzine1.pdf
https://www.seas.ucla.edu/brweb/papers/Journals/BR_Magzine2.pdf
https://www.seas.ucla.edu/brweb/papers/Journals/BR_Magzine3.pdf