@article{701421,
     title = {Cayley transform, outer exponential and spinor norm},
     booktitle = {Proceedings of the Winter School "Geometry and Physics"},
     series = {GDML\_Books},
     publisher = {Circolo Matematico di Palermo},
     address = {Palermo},
     year = {1987},
     pages = {[191]-198},
     mrnumber = {MR0946724},
     zbl = {0652.15022},
     url = {http://dml.mathdoc.fr/item/701421}
}

Lounesto, Pertti. Cayley transform, outer exponential and spinor norm, dans Proceedings of the Winter School "Geometry and Physics", GDML_Books,  (1987), pp. [191]-198. http://gdmltest.u-ga.fr/item/701421/