TY  - JOUR
AU  - McLenaghan, R. G.
TI  - On the validity of Huygens' principle for second order partial differential equations with four independent variables. Part I : derivation of necessary conditions
JO  - Annales de l'institut Henri Poincaré. Section A, Physique Théorique
PY  - 1974
SP  - 153
EP  - 188
VL  - 20
IS  - 2
PB  - Gauthier-Villars
UR  - http://www.numdam.org/item/AIHPA_1974__20_2_153_0/
LA  - en
ID  - AIHPA_1974__20_2_153_0
ER  -