I'm having a hard time finding some references on series solutions for "nonlinear" ODE's, the most I could find was a small excerpt on Wikipedia.

https://en.wikipedia.org/wiki/Power_series_solution_of_differential_equations

Most books just say something along the lines of ... and the method is applicable to nonlinear ODE's. But none I've seen go into detail let alone an example. Can anyone suggest me a good book or reference (in particular for 2nd order nonlinear ODEs)?

Thanks