  Dwarf spheroidal galaxies (dSph) orbiting the Milky Way are complex objects
often with complicated star formation histories and internal dynamics. In this
work, we search for stellar substructures in four of the classical dSph
satellites of the Milky Way: Sextans, Carina, Leo I, and Leo II. We apply two
methods to search for stellar substructure: the minimum spanning tree method,
which helps us to find and quantify spatially connected structures, and the
"brute-force" method, which is able to find elongated stellar substructures. We
detected the previously known substructure in Sextans, and also found a new
stellar substructure within Sextans. Furthermore, we identified a new stellar
substructure close to the core radius of the Carina dwarf galaxy. We report a
detection of one substructure in Leo I and two in Leo II, but we note that we
are dealing with a low number of stars in the samples used. Such old stellar
substructures in dSph galaxies could help us to shed light on the nature of the
dark matter halos, within which such structures form, evolve, and survive.
