@article{701439,
     title = {Conformally invariant wave equations in $3+2$-de Sitter linear gravity},
     booktitle = {Proceedings of the Winter School "Geometry and Physics"},
     series = {GDML\_Books},
     publisher = {Circolo Matematico di Palermo},
     address = {Palermo},
     year = {1989},
     pages = {[179]-194},
     mrnumber = {MR1009571},
     zbl = {0678.53072},
     url = {http://dml.mathdoc.fr/item/701439}
}

Gazeau, J. P.; Hans, M. Conformally invariant wave equations in $3+2$-de Sitter linear gravity, dans Proceedings of the Winter School "Geometry and Physics", GDML_Books,  (1989), pp. [179]-194. http://gdmltest.u-ga.fr/item/701439/