@article{AM2_1980__21_182419,
     author = {P.G. Laird},
     title = {A reconsideration of the },
     journal = {Aequationes mathematicae},
     pages = {98--104},
     publisher = {mathdoc},
     volume = {21},
     year = {1980},
     zbl = {0456.39005},
     url = {http://geodesic.mathdoc.fr/item/AM2_1980__21_182419/}
}