Separatists or Russian troops and local collaborators? Russian aggression in Ukraine : the problem of definitionsTsybulenko, Evhen; Francis, J'Moul A.The use of force against Ukraine and international law : jus ad bellum, jus in bello, jus post bellum2018 / p. 123-144 https://doi.org/10.1007/978-94-6265-222-4_6