The explosion of youth revolts in the long 1970s, including the emergence of environmental activism in western Europe, coincided with the democratization of printing technologies, and led to radical transformation in the production and distribution of knowledge. Publishing became cheap and easy due to the appearance of portable versions of formerly costly and heavy printing machinery and a myriad of self-published zines with an environmentalist tone flourished, disseminating a firm rejection to the post-war consensus of consumerism and growth, denouncing the overarching planning organizations, policies, and strategies. Besides criticism, they also present ways of thinking, living, cooperating, and building that follow different rules and values than consumer capitalism. This contribution identifies a gap in European planning history related to the agency of 1970s' environmental activism and explores the potential of environmentalist zines as sources to sustain historical inquiry and help to fill that gap. It proposes conceptualizing zines as 'minor' sources, arguing that the Deleuzian-Guattarian category is a useful concept for reframing previously marginalized voices in planning history. Through the analysis of seven transnationally published zines, the paper demonstrates their validity as sources that document contributions of voices that have been neglected so far.