Higher-derivative harmonic oscillators: stability of classical dynamics and adiabatic invariantsNicolas Boulanger, Fabien Buisseret, Frédéric Dierick and Olivier WhiteEur. Phys. J. C, 79 1 (2019) 60DOI: https://doi.org/10.1140/epjc/s10052-019-6569-y