https://allthatsinteresting.com/ivan-sidorenko
https://en.wikipedia.org/wiki/Lyudmila_Pavlichenko
https://www.warhistoryonline.com/instant-articles/an-artist-who-became-the-ussrs-most-lethal-sniper-dispatched-over-500-germans.html
https://armyhistory.org/u-s-and-german-field-artillery-in-world-war-ii-a-comparison/
https://en.wikipedia.org/wiki/M1938_mortar
https://historycollection.com/seven-legendary-snipers-of-world-war-2/6/
https://military.wikia.org/wiki/Fyodor_Okhlopkov
https://military.wikia.org/wiki/Lyudmila_Pavlichenko
https://military.wikia.org/wiki/Ivan_Sidorenko
https://www.thoughtco.com/battle-of-moscow-2360444