Some articles on letterists, letterist:

Guy Debord - Involvement With The Letterists
... Debord joined the Letterist International when he was 19 ... The Letterists were led dictatorially by Isidore Isou until a widely agreed upon schism ended Isou's authority ... This schism birthed several factions of Letterists, one of which was decidedly led by Debord upon Gil Wolman's unequivocal recommendation ...