Pro-Russian units in Ukraine connected to Cossak's?

A magazine from the Ukraine reports that at least some of the pro-Russian forces in the eastern Ukraine are connected to the Cossack's. Yes, those Cossack's.

From the identified militants, a few notes can be made from the
following gunmen who appear to be connected to the raids in Sloviansk
and Kramatorsk. For one, not all are from Russia.

While some may be local radicals, others appear to