Lelyakov, O. P., Karpenko, A. S. and Babadzhan, R.-D. O. (2018) “Dynamics of a Non-Rotating Test Null String in the Gravitational Field of a Closed ‘Thick’ Null String Radially Expanding or Collapsing in the Plane z = 0”, Ukrainian Journal of Physics, 59(11), p. 1114. doi: 10.15407/ujpe59.11.1114.