پیرامون برخی خمینه‌های همدیس اینشتین از بعد چهار

[1] H. W. Brinkmann, Riemann spaces conformal to Einstein spaces, Math. Ann., 91 (1924) 269–278.
[2] H. W. Brinkmann, Einstein spaces which are mapped conformally on each other, Math. Ann., 94 (1925) 119–145.
[3] G. Calvaruso, Homogeneous structures on three-dimensional Lorentzian manifolds, J. Geom. Phys., 57 (2007) 1279–1291.
[4] G. Calvaruso and A. Zaeim, Four-dimensional homogeneous Lorentzian manifolds, Monatsh Math., 174 (2014) 377–402.
[5] G. Calvaruso and A. Zaeim, Symmetries of Lorentzian three-manifolds with recurrent curvature, SIGMA, 12 (2016) 63–75.
[6] G. Calvaruso and A. Zaeim, A complete classification of Ricci and Yamabe solitons of non-reductive homogeneous 4-spaces, J. Geom. Phys., 80 (2014) 15–25.
[7] G. Calvaruso and A. Zaeim, Geometric structures over non-reductive homogeneous 4-spaces, Adv. Geom., 14 (2014) 191–214.
[8] G. Calvaruso and A. Zaeim, On the symmetries of the Lorentzian oscillator group, Collect. Math., 68 (2017) 51–67.
[9] G. Calvaruso, Oscillator spacetimes are Ricci solitons, Nonlinear Anal., 140(2016) 254–269.
[10] G. Calvaruso and A. Zaeim, Conformal geometry of semi-direct extensions of the Heisenberg group, Jour. Math. Phys. Anal. Geom., 14 (2021) 407–421.
[11] G. Calvaruso and A. Zaeim, Geometric structures over four-dimensionl generelized symmetric spacse, Mediterr. J. Math., 10 (2013) 971–987.
[12] G. Calvaruso and E. Rosado, Ricci solitons on low-dimensional generalized symmetric spaces, J. Geom. Phys., 112 (2017) 106–117.
[13] E. Calviño-Louzao, E. García-Río, I. Gutiérrez-Rodríguez and R. Vázquez-Lorenzo, Conformal geometry of non-reductive four-dimensional homogeneous spaces, Math. Nachr., 290 (2017) 1470–1490.
[14] J. Cerny and O. Kowalski, Classification of generalized symmetric pseudo-Riemannian spaces of dimen-sion n ≤ 4, Tensor (N.S.), 38 (1982) 256–267.
[15] M. Chaichi and A. Zaeim, Locally Homogeneous Four-Dimensional Manifolds of Signature (2, 2), Math. Phys. Anal. Geom., 16 (2013) 345–361.

[16] B. De Leo and J. Van der Veken, Totally geodesic hypersurfaces of fourdimensional generalized sym-metric spaces, Geom. Dedicata, 159 (2012) 373–387.
[17] E. Garcia-Rio, P. B. Gilkey and S. Nikcevic, Homogeneity of Lorentzian three-manifolds with recurrent curvature, Math. Nachr., 287 (2014) 32–47.
[18] R. Gover and P. Nurowski, Obstructions to conformally Einstein metrics in n dimensions, J. Geom. Phys., 56 (2006) 450–484.
[19] C. N. Kozameh, E. T. Newman and K. P. Tod, Conformal Einstein spaces, Gen. Rel. Grav., 17 (1985)
343–352.
[20] W. Kuhnel and H. B. Rademacher, Conformal transformations of pseudo-Riemannian manifolds, Recent developments in pseudo-Riemannian geometry, ESI Lect. Math. Phys., Eur. Math. Soc., Zurich, (2008) 261–298.
[21] W. Kuhnel and H. B. Rademacher, Conformally Einstein spaces revisited, Pure and Appl. Differential Geom. PADGE 2012 - In Memory of Franki Dillen, (2013) 161–167.
[22] B. O’Neill, Semi-Riemannian Geometry, Pure and Applied Mathematics, 103, Academic Press, Inc. Harcourt Brace Jovanovich, Publishers, New York 1983.
[23] F. Tricerri and L. Vanhecke, Homogeneous structures on Riemannian manifolds, in: London Math. Soc. Lect. Notes, 83, Cambridge Univ. Press, 1983.