1. [1] V. A. Belinskii: L-A pair of a system of coupled equations of gravitational and electromagnetic fields, JTEP Lett. 30, 1979, 28-31.
2. [2] V. A. Belinskii and V. E. Zakharov: Integration of the Einstein equations by means of the inverse scattering problem technique, Sov.Phys. JETP 48, 1978, 985-994.
3. [3] K. Nagatomo: Formal power series solutions of the stationary axisymmetric vacuum Einstein equations, Osaka J. Math. 25, 1988, 49-70.
4. [4] Y. Nakamura: On a linearization of the stationary axially symmetric Einstein equations, Class. Quantum Grav. 4, 1987, 437-440.