Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The communist propaganda was extensively based on the Marxism-Leninism ideology to promote the Communist Party line. In societies with pervasive censorship, the propaganda was omnipresent and very efficient. It penetrated even social and natural sciences giving rise to various pseudo-scientific theories like Lysenkoism, whereas fields of real knowledge, as genetics, cybernetics, and comparative linguistics were condemned and forbidden as "bourgeois pseudoscience". With "truths repressed, falsehoods in every field were incessantly rubbed in in print, at endless meetings, in school, in mass demonstrations, on the radio".