Navarro Helio A,Cveticanin Livija J (2018) Extension of the Hamiltonian Approach with General Initial Conditions, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, vol. 56, br. 1, str. 255-267 (Article) Navarro Helio A,Cveticanin Livija J (2016) Amplitude-frequency relationship obtained using Hamiltonian approach for oscillators with sum of non-integer order nonlinearities, APPLIED MATHEMATICS AND COMPUTATION, vol. 291, br. , str. 162-171 (Article)