@inbook{inbook9e42d0b1,
title   = {Periodic trajectories of dynamical systems having a one-parameter group of symmetries},
author = {Giambó, Roberto and Piccione, Paolo},
year = {2017},
doi = {10.2991/2F978-94-6239-240-3_2},
publisher = {Atlantis Press},
journal   = {Topics in modern differential geometry}
}