Challenger 2 vs Leopard 2

SOURCES:
http://www.fprado.com/armorsite/chall2.htm
https://defenseissues.net/2015/09/21/nato-main-battle-tanks-comparison/
https://www.stripes.com/news/germany-s-leopard-tanks-prove-vulnerable-in-islamic-state-fight-1.449278#.WR2goGTytn0
https://www.army.mil/article/177819/us_army_europe_to_increase_presence_across_eastern_europe
http://uk.reuters.com/article/uk-germany-qatar-tanks-idUKBRE96D05E20130714
https://www.theguardian.com/commentisfree/2011/jul/09/germany-arms-sale-saudi-arabia
Gelbart, Marsh (1996). Tanks: main battle and light tanks. p. 19
http://www.globalsecurity.org/military/systems/ground/mbt-70.htm
Foss, Christopher F (2002), Jane's Tanks and Combat Vehicles Recognition Guide, New York: HarperCollins, p. 35
http://www.kmweg.com/
http://www.army-technology.com/projects/leopard/
https://defenseissues.net/2015/09/21/nato-main-battle-tanks-comparison/
http://www.army.mod.uk/equipment/23236.aspx
http://www.defensenews.com/story/defense/land/vehicles/2016/01/16/uk-surges-ahead-challenger-2-upgrade/78841260/
http://www.armyrecognition.com/germany_german_army_heavy_armoured_vehicle_tank_uk/leopard_2a4_main_battle_tank_technical_data_sheet_specifications_description_pictures_video.html
http://www.army-technology.com/projects/leopard/
https://www.youtube.com/watch?v=OlegqcKpdXs
http://nationalinterest.org/blog/the-buzz/get-ready-russia-european-power-has-plans-lethal-new-tank-15251
http://www.defensenews.com/story/defense/land/vehicles/2016/01/16/uk-surges-ahead-challenger-2-upgrade/78841260/