1. Binz, E., Śniatycki, J., Fischer, H.R.: Geometry of Classical Fields, North-Holland Mathematics Studies, vol. 154. North-Holland, Dordrecht (1998)
2. Bleecker, D.: Gauge Theories and Variational Principles. Addison-Wesley, Reading (1981)
3. Bourbaki, N.: Groupes et algèbres de Lie, Hermann, Paris, Ch. I (2nd ed.), 1971; Ch. II–III, 1972; Ch. IV–VI, 1968; Ch. VII–VIII (1974)
4. Calvaruso, G., Fino, A.: Four-dimensional pseudo-Riemannian homogeneous Ricci solitons. Int. J. Geom. Methods Mod. Phys. 12(5), 1550056 (2015)
5. Calvaruso, G., Van der Veken, J.: Totally geodesic and parallel hypersurfaces of four-dimensional oscillator groups. Results Math. 64(1–2), 135–153 (2013)