P. Baird, Riemannian twistors and Hermitian structures on low???dimensional space forms, Journal of Mathematical Physics, vol.33, issue.10, pp.3340-3355, 1992.
DOI : 10.1063/1.529935

P. Baird and J. C. Wood, A spinor formulation for harmonic morphisms, Twistor Newsletter, pp.31-2937, 1990.

P. Baird and J. C. Wood, Monopoles, harmonic morphisms and spinor fields, Further Advances in Twistor Theory Integrable systems, conformal geometry and gravitation, Pitman Research Notes in Math, vol.232, pp.49-62, 1995.

P. Baird and J. C. Wood, Harmonic morphisms, conformal foliations and shear-free ray congruences, Bull. Belg. Math. Soc. Simon Stevin, vol.5, issue.4, pp.549-564, 1998.

P. Baird and J. C. Wood, Harmonic Morphisms Between Riemannian Manifolds, Soc. Monogr.(N.S), 2003.
DOI : 10.1093/acprof:oso/9780198503620.001.0001

B. Fuglede, Harmonic morphism between semi-riemannian manifolds, Ann. Acad. Sci. Fennicae, vol.21, pp.31-50, 1995.

B. Fuglede, Harmonic morphisms between riemannian manifolds, Annales de l???institut Fourier, vol.28, issue.2, pp.107-151, 1978.
DOI : 10.5802/aif.691

R. Penrose and W. Rindler, Spinors and Space-Time Volume2, 1986.

R. Penrose, Twistor Algebra, Journal of Mathematical Physics, vol.8, issue.2, pp.345-366, 1967.
DOI : 10.1063/1.1705200

J. C. Wood, Harmonic morphisms and hermitien structures on Einstein 4-manifols, International Journal of Mathematics, vol.3, pp.515-439, 1992.

M. Wehbe, Aspects twistoriels des applications semi-conformes, Thesis