Good article from 1987 explaining that the use of the term "dictatorship of the proletariat" in German by Marx and Engels is not the same as the English word "dictatorship" and does not conflict with democracy.
Engels' 1884 book focusing on early human history, following the disintegration of the primitive community and the emergence of a class society based on private property. Engels looks into the origin and essence of the state, and concludes it is bound to wither away leaving a classless society.
From workers autonomy to social autonomy: the experience of Socialisme ou Barbarie. An interview with Daniel Blanchard - Amador Fernández-Savater
Epub of Marx's Draft of an Article on Friedrich List’s book: Das Nationale System der Politischen Oekonomie. Text taken from marxists.org.
Epub of Marx's Comments on James Mill. Text taken from marxists.org.
Epub of Marx's Second Draft of Critique of Political Economy. Text taken from marxists.org.
Epub of Marx's Drafts for The Civil War in France. Text taken from marxists.org.