Fj. Herranz et al., CAYLEY-KLEIN ALGEBRAS AS GRADED CONTRACTIONS OF SO(N+1), Journal of physics. A, mathematical and general, 27(7), 1994, pp. 2515-2526
We study Z2 XN graded contractions of the real compact simple Lie alge
bra so(N + 1), and we identify within them the Cayley-Klein algebras a
s a naturally distinguished subset.