Berg A. Theory and Calculation of Lamp Generators. C1. Independent excitation of persistent oscillations In Russian (ask us if in doubt)/Berg A. Teoriya i raschet lampovykh generatorov. Ch1. Nezavisimoe vozbuzhdenie nezatukhayushchikh kolebaniy ONTI NKTP 1935. 314 p. SKUalb459295c3cc070d6e.