“…They introduced symbol classes and symbolic calculus for matrix-valued symbols on compact Lie groups and presented plentiful applications of this global theory. After that, the theory of pseudo-differential operators with matrix-valued symbols on compact (Hausdorff) groups, compact homogeneous spaces, compact manifolds is broadly studied by several authors [3,4,5,9,11,12,13,14,15,20,30,31,33,34,38,44] in many different contexts.…”