[2] Jacobson, N.: 
Structure and representations of Jordan algebras. AMS Providence, Rhode Island, 1968. 
MR 0251099 | 
Zbl 0218.17010[3] Kadison, R. V., Pedersen, G. K.: 
Means and convex combinations of unitary operators. Math. Scand. 57 (1985), 249–266. 
MR 0832356 | 
Zbl 0573.46034[4] Rørdam, M.: The theory of unitary rank and regular approximation. Ph.D. thesis, University of Pennsylvania, 1987.
[5] Rørdam, M.: 
Advances in the theory of unitary rank and regular approximations. Ann. of Math. (2) 128 (1988), 153–172. 
MR 0951510[6] Siddiqui, A. A.: Computation of the $\lambda _{u}$–function in $JB^{*}$–algebras. submitted.
[7] Siddiqui, A. A.: 
Asymmetric decompositions of vectors in $JB^{*}$–algebras. Arch. Math. (Brno) 42 (2006), 159–166. 
MR 2240353 | 
Zbl 1164.46342[8] Siddiqui, A. A.: 
On unitaries in $JB^{*}$–algebras. Indian J. Math. 48 (1) (2006), 35–48. 
MR 2229466 | 
Zbl 1115.46058[12] Siddiqui, A. A.: 
A proof of the Russo–Dye theorem for $JB^{*}$–algebras. New York J. Math. 16 (2010), 53–60. 
MR 2645985 | 
Zbl 1231.46015[13] Siddiqui, A. A.: 
Convex combinations of unitaries in $JB^{*}$–algebras. New York J. Math. 17 (2011), 127–137. 
MR 2781910 | 
Zbl 1227.46035[14] Siddiqui, A. A.: 
The $\lambda _{u}$–function in $JB^{*}$–algebras. New York J. Math. 17 (2011), 139–147. 
MR 2781911 | 
Zbl 1227.46036