Fascism
In her work, The Origins of Totalitarianism, published in 1951, Hannah Arendt compared National Socialism, Stalinism and Maoism. She does not talk about these regimes being fascist; according to her, they are totalitarian. In 1967, German philosoper Jürgen Habermas warned about a "left-wing fascism" of a protest movement in Germany of the 1960s, commonly known as Ausserparlametarische Opposition, or APO.