Multiple solutions and corresponding power output of a nonlinear bistable piezoelectric energy harvesterArkadiusz Syta, Grzegorz Litak, Michael I. Friswell and Sondipon AdhikariEur. Phys. J. B, 89 4 (2016) 99DOI: https://doi.org/10.1140/epjb/e2016-60699-0