TY  - JOUR
AU  - Anderson, W. G.
AU  - McLenaghan, R. G.
TI  - On the validity of Huygens' principle for second order partial differential equations with four independent variables. II. A sixth necessary condition
JO  - Annales de l'I.H.P. Physique théorique
PY  - 1994
SP  - 373
EP  - 432
VL  - 60
IS  - 4
PB  - Gauthier-Villars
UR  - http://archive.numdam.org/item/AIHPA_1994__60_4_373_0/
LA  - en
ID  - AIHPA_1994__60_4_373_0
ER  -