The paper “Nonlinear perturbations of Hill’s systems and the pendulum with variable length“, co-authored by Michele Bartuccelli and Guido Gentile (Roma II, and Visiting Professor at Surrey), has been published in the Journal of Mathematical Analysis and Applications. It is published open access and the link is here. The paper is on the dynamics of the pendulum with variable length, which has many open questions. The paper of Michele and Guido sheds a bit of light by using some powerful theorems of Hill’s type. In addition, they do nonlinear perturbations of this system in the periodic and quasi-periodic case. The front page, with abstract, of the published paper is shown below (click on image to enlarge).