  The present paper is a continuation of our work [11], where we introduced a
fractional operator calculus related to a fractional ${\psi}-$Fueter operator
in the one-dimensional Riemann-Liouville derivative sense in each direction of
the quaternionic structure, that depends on an additional vector of complex
parameters with fractional real parts.
  This allowed us also to study a pair of lower order fractional operators and
prove the associated analogues of both Stokes and Borel-Pompieu formulas for
holomorphic functions in two complex variables.
