Quotation from the "Critique of the Gotha Programme" by Karl Marx (哥达纲领批判 - originally published in 1891 as Kritik des Gothaer Programms). In this text, Marx developed his concept of the dictatorship of the proletariat. This concept was central in the "Study Theory" campaign of 1975.
The quotation:
"In between a capitalist society and a communist society is a period of revolutionary transformation where the former turns into the latter. This corresponds to the political transitional period, a state of this period cannot be something else than the revolutionary proletarian dictatorship."