G. Hall, “Some developments of Petrov's work on conformal and projective structure”, Учен. зап. Казан. ун-та. Сер. Физ.-матем. науки, 153:3 (2011), 175–184
2009
2.
Graham S. Hall, David P. Lonie, “Holonomy and Projective Equivalence in 4-Dimensional Lorentz Manifolds”, SIGMA, 5 (2009), 066, 23 стр.
