Pyotr Alexeyevich Kropotkin (Пётр Алексеевич Кропоткин, other spelling: Pëtr Kropotkin, Pierre Kropotkine), who described him as "a man with a soul of that beautiful white Christ which seems coming out of Russia." He wrote many books, pamphlets and articles, the most prominent being The Conquest of Bread and Fields, Factories and Workshops, and his principal scientific offering, Mutual Aid: A Factor of Evolution. He was also a contributor to the Encyclopædia Britannica Eleventh Edition.