@article{MAN_1974__211_162657,
     author = {B. Scarpellini},
     title = {On the {Spectra} of {Certain} {Semi-Groups.}},
     journal = {Mathematische Annalen},
     pages = {323--336},
     publisher = {mathdoc},
     volume = {211},
     year = {1974},
     zbl = {0291.47021},
     url = {http://geodesic.mathdoc.fr/item/MAN_1974__211_162657/}
}