@article{articlede3011ca,
title   = {An extension of a theorem of Schoenberg to products of spheres},
author = {Guella, J. C and Menegatto, Valdir Antônio and Peron, Ana Paula},
year = {2016},
doi = {10.1215/17358787-3649260},
journal   = {Banach Journal of Mathematical Analysis}
}