Ryan, F. (1976). Four Days for Four Years: The Shortened Work Week Works.
Citazione stile Chigago Style (17a edizione)Ryan, Frederick. Four Days for Four Years: The Shortened Work Week Works. 1976.
Citatione MLA (9a ed.)Ryan, Frederick. Four Days for Four Years: The Shortened Work Week Works. 1976.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.