@article{article91c70001,
title   = {Class of C∞-integrable Hamiltonian systems},
author = {Oliva, Waldyr Muniz and Castilla, Maria Stella Amorim Coutinho},
year = {1989},
doi = {10.1017/S0308210500024161},
journal   = {Proceedings of the Royal Society of Edinburgh,Section A: Mathematics}
}