The Two-stage Mechanical Oscillator of Veljko Milkovic.

https://www.pendulum-lever.com/two-stage-oscillator.html

http://www.veljkomilkovic.com/indexEng.htm

https://www.vemirc.com/en/homepage/

https://web.archive.org/web/20200705161811/http://free-energy.ws/veljko-milkovic/

https://web.archive.org/web/20191221052302/http://veljkomilkovic.com/Images/Opinion_Dr_Peter_Lindemann.PDF