“…According to the Radon-Hurwitz theorem in the Appendix B, for k = 7 − r 7 = 4, one aims the set {e I 1 , e I 2 , e I 3 , e I 4 } ⊂ Cℓ 0,7 that commute and squares the identity [28]. Identifying, for example [29] is a primitive one. Hence, a spinor ψ ∈ S 7 has its algebraic version as the elementψf of the left ideal Cℓ 0,7 f , for some multivectorψ ∈ Cℓ 0,7 .…”