@article{10_4064_cm_29_1_71_81,
     author = {Robert W. Quackenbush},
     title = {Some classes of idempotent functions and their compositions},
     journal = {Colloquium Mathematicum},
     pages = {71--81},
     publisher = {mathdoc},
     volume = {29},
     number = {1},
     year = {1974},
     doi = {10.4064/cm-29-1-71-81},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-29-1-71-81/}
}