On monogenic mappings of the quaternionic variables
  In the paper [1] we consider a new class, so-called, $G$-monogenic (differentiable in the sense of Gateaux) quaternionic mappings. In the present paper we introduce quaternionic $H$-monogenic (differentiable in the sense of Hausdorff) mappings and establish the relation between $G$-monogenic and $H$-monogenic mappings. The equivalence of different definitions of $G$-monogenic mapping is proved. 
V. S. Shpakivskyi, T. S. Kuzmenko
math.CV