@article{AIHPA_1977__26_3_323_0,
     author = {McLenaghan, R. G.},
     title = {Addendum \`a {\guillemotleft} {R.} {G.} {McLenaghan} : on the validity of {Huygens'} principle for second order partial differential equations with four independent variables. {I} {\guillemotright}},
     journal = {Annales de l'institut Henri Poincar\'e. Section A, Physique Th\'eorique},
     pages = {323--323},
     publisher = {Gauthier-Villars},
     volume = {26},
     number = {3},
     year = {1977},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1977__26_3_323_0/}
}