Before revision: Cog's Ladder of group development is based on the work, "Cog's Ladder: A Model of Group Growth", by George O. Charrier, an employee of Procter and Gamble, published in a company newsletter in 1972.
After revision: Cog's ladder of group development is based on the work, "Cog's Ladder: A Model of Group Growth", by George O. Charrier, an employee of Procter and Gamble, published in a company newsletter in 1972.