Buyukliev, Nikolaj. 1999. “K-Theory of the $C^*$-Algebra of Multivariable Wiener-Hopf Operators Associated With Some Polyhedral Cones in $R^n$”. Ann. Sofia Univ. Fac. Math. And Inf. 91 (December):115-25. https://stipendii.uni-sofia.bg/index.php/fmi/article/view/274.