“Leninism is Marxism of the era of imperialism and the proletarian revolution. To be more exact, Leninism is the theory and tactics of the proletarian revolution in general, the theory and tactics of the dictatorship of the proletariat in particular. Marx and Engels pursued their activities in the pre-revolutionary period (we have the proletarian revolution in mind), when developed imperialism did not yet exist, in the period of the proletarians' preparation for revolution, in the period when the proletarian revolution was not yet an immediate practical inevitability. But Lenin, the disciple of Marx and Engels, pursued his activities in the period of developed imperialism, in the period of the unfolding proletarian revolution, when the proletarian revolution had already triumphed in one country, had smashed bourgeois democracy and had ushered in the era of proletarian democracy, the era of the Soviets.”

Source: Red Horizons: Chronicles of a Communist Spy Chief, p. 47

Directives on the Cultural Revolution (1966-1972)

Source: The Birth of Fascist Ideology: From Cultural Rebellion to Political Revolution, 1994, p. 27

The War and Russian Social-Democracy (September 1917), The Lenin Anthology
1910s

Collected Works, Vol. 30, pp. 52–62.
Collected Works

(1847)

Source: Directives on the Cultural Revolution (1966-1972)

Letter to Philipp Van Patten http://www.marxists.org/archive/marx/works/1883/letters/83_04_18.htm (18 April 1883)