Sorrell, Ian High energy asymptotics and trace formulas for the perturbed harmonic oscillator High energy asymptotics and trace formulas for the perturbed harmonic oscillator untagged;Mathematical Sciences not elsewhere classified 2013-08-19
    https://repository.lboro.ac.uk/articles/thesis/High_energy_asymptotics_and_trace_formulas_for_the_perturbed_harmonic_oscillator/9373907