A very interesting book… http://readingbookstoknowourselves.com/2019/03/25/marcus-malte-%cf%84%ce%bf-%ce%b1%ce%b3%cf%8c%cf%81%ce%b9-%ce%b5%ce%ba%ce%b4%cf%8c%cf%83%ce%b5%ce%b9%cf%82-opera-2019/

https://www.youtube.com/watch?v=-whS3PD53qE

http://readingbookstoknowourselves.com/2019/03/25/marcus-malte-%cf%84%ce%bf-%ce%b1%ce%b3%cf%8c%cf%81%ce%b9-%ce%b5%ce%ba%ce%b4%cf%8c%cf%83%ce%b5%ce%b9%cf%82-opera-2019/