@article{JRAM_1990__408_153241,
     author = {E. Horozov},
     title = {Perturbations of the spherical pendulum and {Abelian} integrals.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {114--135},
     publisher = {mathdoc},
     volume = {408},
     year = {1990},
     zbl = {0692.58031},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1990__408_153241/}
}