The different solutions of the partial differential equations and the comparing of them K. Orlov (1978) Matematički Vesnik
The Propagation of Singularities along Gliding Rays. R.B. Melrose, K.G. Andersson (1977) Inventiones mathematicae
The propagation of singularities for pseudo-differential operators with self-tangential characteristics N. Dencker (1987/1988) Séminaire Équations aux dérivées partielles (Polytechnique)
The shape and smoothness of stable plasma configurations David Kinderlehrer, Joel Spruck (1978) Annali della Scuola Normale Superiore di Pisa - Classe di Scienze
Travaux de Melrose sur le problème des «glancing rays» V. Guillemin (1975/1976) Séminaire Équations aux dérivées partielles (Polytechnique)