is sometimes called Dirac operator in k Clifford variables. In the notation, S is the space of spinors, x i = ( x i 1 , x i 2 , … … , x i n ) are n -dimensional variables and ∂ ∂ x i _ _ = ∑ ∑ j e j ⋅ ⋅ ∂ ∂ x i j is the Dirac operator in the i -th variable. This is a common generalization of the Dirac operator (k = 1) and the Dolbeault operator (n = 2, k arbitrary). It is an invariant differential operator, invariant under the action of the group SL(k) × Spin(n). The resolution of D is known only in some special cases.