@article {boscaggin2012periodic,
	title = {Periodic solutions to superlinear planar Hamiltonian systems},
	journal = {Portugaliae Mathematica},
	volume = {69},
	number = {2},
	year = {2012},
	pages = {127{\textendash}141},
	publisher = {European Mathematical Society Publishing House},
	abstract = {<p>We prove the existence of infinitely many periodic (harmonic and subharmonic) solutions to planar Hamiltonian systems satisfying a suitable superlinearity condition at infinity. The proof relies on the Poincare-Birkhoff fixed point theorem.</p>},
	author = {Alberto Boscaggin}
}
