Nonexistence of Petrov type III space-times on which Weyl's neutrino equation or Maxwell's equations satisfy Huygens' principle R. G. McLenaghan; F. D. Sasse — 1996 Annales de l'I.H.P. Physique théorique
Complete solution of Hadamard's problem for the scalar wave equation on Petrov type III space-times S. R. Czapor; R. G. McLenaghan; F. D. Sasse — 1999 Annales de l'I.H.P. Physique théorique
Huygens' principle for the non-self-adjoint scalar wave equation on Petrov type III space-times W. G. Anderson; R. G. McLenaghan; F. D. Sasse — 1999 Annales de l'I.H.P. Physique théorique