@article{AIHPA_1969__11_2_207_0,
     author = {Tugov, I. I.},
     title = {Conformal covariance and invariant formulation of scalar wave equations},
     journal = {Annales de l'institut Henri Poincar\'e. Section A, Physique Th\'eorique},
     pages = {207--220},
     publisher = {Gauthier-Villars},
     volume = {11},
     number = {2},
     year = {1969},
     mrnumber = {250622},
     language = {en},
     url = {http://www.numdam.org/item/AIHPA_1969__11_2_207_0/}
}